Tomato Pudding (AKA Pie) - A Shaker Recipe

I laughed when I realized my last six posts were all about desserts or sort-of-desserts.  My sweet tooth obviously took control of my decision-making process!  So I went on a search for something more savory to prepare.

I'm still exploring The Best of Shaker Cooking by Amy Bess Miller and Persis Fuller.  With over 900 recipes, you can understand why it takes time to peruse.  There are so many temptations!  I found a recipe for lamb shanks I would love to make; it is almost time to find lamb shanks in the stores.  Fingers are crossed.

ISBN 0-02-584980-8

This recipe comes from the Vegetable section (See?  No desserts!).  There are twelve tomato recipes; within the recipes they have a quote from a Shaker sister:  "We have tomatoes for every meal -- fried for breakfast, stewed for dinner, soup for supper."  The Shakers were good gardeners and good cooks - which I envy - and their tomato recipes show us how to fry and stew them, but also how to bake and broil them, as well as making dumplings, custard, pie, puddings, salad, and toast.

The recipe specifically labeled as "pie" is basically sliced tomatoes bound together with a mixture of sugar, cream, egg, and nutmeg, and placed between two crusts.  

The recipe I tried is called a pudding.  It is a cooked filling on top of buttered crumbs and topped with a crust.  They offer a second pudding recipe that is similar, using bread cubes on the bottom, crumbs on the top, and the filling has more herbs.  I chose the simpler one to see what the filling is like without all the extras.  Besides, it is fun to make pie crust.  

The recipe source is credited to the Hancock Shaker Village.  Click here to visit their website.

Tomato Pudding (page 158)

4 cups canned tomatoes cooked down to 2 cups

1 cup light brown sugar

1 tablespoon grated onion

1/2 teaspoon salt

1/4 teaspoon pepper

1 cup bread crumbs

1/2 cup melted butter

1 pastry lid for 8 inch pie plate

Combine first 5 ingredients and bring to a boil.  Simmer to thicken.  

In an 8-inch pie dish put bread crumbs, cover with butter, top with tomato mixture, and cover with pastry crust.  Bake in 350 degree F oven for 30 minutes.  Watch to see that bottom doesn't burn (use tip of knife to lift up crust).  Tomatoes burn easily.  Serves 4 - 6.

My Notes

First I made the pie crust dough and let it rest in the refrigerator while I did everything else.

The three cans of diced tomatoes yielded 43.5 ounces instead of the 4 cups = 32 ounces asked for in the recipe.  I decided to use it all and reduce to about half.

Being cautious about burning the tomatoes while reducing them, I keep the heat on very low for a long time.  This wasn't really reducing the quantity, so I turned the heat up after a few hours but watched it carefully and stirred it to make sure nothing was sticking on the bottom.

When it reduced to just under 3 cups (not quite half), I decided it was time to add the other flavors.  I adjusted their measures up a little to match the greater tomato quantity. (Not the sugar.)

To be honest, I was surprised at the amount of sugar listed in the recipe.  (Not that I was complaining, and still not a dessert!)  I wondered if it could be lowered and still taste good.

I also started preheating the oven at this point.

The instructions said to bring to a boil and simmer to thicken, so I put it on medium heat until it started to boil and then put it down to low to just a bare simmer.  I decided that "to thicken" meant to dissolve the sugar and to give the flavors a chance to infuse.  I wasn't sure it would thicken up much more.

It actually did thicken a little more (or was it my imagination?) and it tasted good.  I liked the hint of pepper.  It was a bit sweeter than I expected for a savory recipe.

The bread crumbs made a thick base in the pie pan.

There were no directions to mix the crumbs and the melted butter, just to cover the crumbs.  So I did!  I just poured the butter over the crumbs.

And then I poured the filling over it all.

You can see how full the pan was, which shouldn't have surprised me considering I made more filling that the recipe called for.  I decided it was acceptable because all that was left was to place the crust.

The filling was still very hot and I worried that the crust would be melted if it took me too long to get it "just right" once it was in place.

So I rolled the chilled crust and used an 8 inch cake pan as a guide for where to cut the crust to fit the pie pan.

Leaving an allowance for a decorative edge.

Then I flipped the crust on top of the hot filling and went to work to form the edge.  Boy, did I work quickly!

And then I popped it into the hot oven and set the timer for 30 minutes.

I checked it "using the tip of a knife", barely lifting the crust to see how the filling looked.  It darkened but did not look or smell burned.  I checked after 20 and after 25 minutes of cooking.  

It did overflow the pan - again, not surprising - but I had another pan underneath to catch the drips.

At 30 minutes the crust was nicely browned and it all smelled good.

I let the pie cool to lukewarm before serving.

The Verdict

Cooling allowed the filling to set up and firm before slicing.

I was impressed at how well the layers showed and stayed distinct.

I was also pleased that the tomatoes didn't burn.

I served it with a tossed green salad and a little sliced pork on the side.  It was nice to have the meat be a side dish in this meal.

As for the flavor:  it was good!  A distinctly tomato flavor, with some savory from the pepper and possibly from the onion.  The filling was very moist but not runny.  The top crust added a rich mouthfeel and a crispy crunch.  The bottom crumbs layer added a more chewy crunch, just like a similar crust you find on cheesecakes. 

Success!

Yes, it was sweet but not overly so.  I think you could reduce the sugar by at least 1/4 cup and still have a good result.  

My guest taster thought it was just right as it was.  I loved it, too, but I think it would be better with more pepper and some lemon zest.  The second tomato pudding recipe calls for more onion and adds parsley and basil, and a lot less sugar (lists 1/4 cup).  That would be good, too, and make it more savory.

We enjoyed the leftovers warmed up the next day.

Chocolate Puffs, a Train Recipe

When I travel, my souvenirs tend to be cookbooks.  Why not?  They are fun and useful memories of the journey, and I can "revisit" the trip when I cook.  

Today's recipe is from a cookbook I bought when in Sacramento, touring the California Railroad Museum.  This book contains recipes from the famed "Harvey Houses", which were a creation of Fred Harvey.  His company provided restaurants located along the train routes, where people could get off the train and have a nice meal in a clean place with pleasant servers:

In the 1870s, people traveling west of the Mississippi were still venturing into the wild.  Loud, smoke-belching trains might have cut across the rough terrain, but the harsh weather, rigid seats, and short breaks for bad food in the middle of nowhere showed that the West was by no means won.  Entrepreneur Fred Harvey had an eye for such problems and a nerve for the impossible.  In 1876, he began establishing high quality dining rooms along the Santa Fe Railroad, and his Harvey Houses helped change the entire picture of the American West. 

... Suddenly, after surging through mountain snow or sweltering heat, rail travelers halted at a surprising sight:  a Harvey House arose out of nowhere and served them like royalty.  Fine china, Irish linen ... and, oh, the "Harvey Girls."  Magical and romantic in a region still rough-edged and rowdy, these polished young servers made the Western rail dining experience a true pleasure.

Some of the sites were developed further into beautiful hotels and resort destinations complete with tours.  It was the advent of air travel, automobiles, and faster trains needing to make fewer stops that is attributed to the demise of the business, which I find sad.  

There are many recipes I would like to try in The Harvey House Cookbook by George H. Foster and Peter C. Weiglin.  Chocolate Puffs, on page 108, is credited to chef George Burnickel, who worked on the California Limited.  

ISBN 978-1-58979-321-7

Chocolate Puffs

1 cup flour

1 oz. melted chocolate

1 cup water

3 eggs

1/2 cup butter

Strawberry preserves

Whipped cream

Boil together one cupful of flour, one cupful of water, and half a cup of butter.  Remove from the fire and beat in an ounce of melted chocolate and three eggs (one at a time).  Bake in a gem pan, and when done cut off the top and put into each cake a teaspoonful of strawberry preserves.  Cover with whipped cream, sweetened and flavored.

And water.

My Notes

I didn't have strawberry preserves but I did have a most marvelous pomegranate jelly made by my friend, MR.  I thought it would go well with chocolate.  Also, I had no whipped cream.

A gem pan is a muffin tin, so I used my regular sized, non-stick muffin tin.  

Mr. Burnickel did not specify an oven temperature, probably expecting that anyone reading the instructions would have experience in knowing the right one, so I did a little reading on the side.  The recipe looked like a choux paste and the word "puff" in the name gave me enough hints on what to do.  I preheated my oven to 400 degrees F.

The chocolate was melted in the microwave (with some left over for nibbling!).  The butter was frozen so I was reluctant to put the flour-water-butter mixture over a high heat for boiling.  I wanted the butter to have a chance to melt.  The three ingredients went over a medium heat, and I stirred it a lot until it all came together and didn't stick to the sides of the pan any more.

Pre-chocolate

Then I turned off the fire and mixed in the chocolate until that mixture looked smooth and well-blended.  After that, the eggs, beating in each one until the mixture looked smooth before adding the next.

With chocolate and eggs.

I used a ladle to scoop the batter into each pan.  I wasn't sure how much they would puff so I filled the cups about halfway to 2/3 full.  That left me with one empty cup, which I filled with water.  (This is recommended to keep balance in the way the pan heats.)

My reading suggested cooking them at 400 degrees F and then reducing the temperature to 350 degrees F.  I cooked them for 12 minutes at 400, which made them puff nicely, and then 23 minutes at 350.  The recommendation was to remove them only after they were "very firm."

I managed to keep the over door closed until about 20 minutes into the 350 degree cooking slot.  Then it was briefly opened for me to poke it, checking for firmness.  They browned well and didn't burn, and they smelled lovely.

I wanted to take them from the pan immediately so they could cool on a rack.  They all stuck to my non-stick pan!  So I let them cool completely in the pan and pulled them out later with the help of a small metal spatula.  

The Verdict

Some of the puffiness had left my cooled chocolate puffs, but they didn't sink down to anything embarrassing.  The bottoms tore when I took them from the pan, so I didn't cut off the tops for serving, I just turned them over.

The texture inside looked just right.

The interior was visibly moist and the "feel" of the puff was delicate and tender.

I served it with a spoonful of pomegranate jelly on top.  The jelly looked like a jewel.

My guest taster noted that the exterior was a little crispy and the interior was moist and tender - very nice!  The chocolate flavor was subtle but pleasantly there, and the pomegranate jelly (tart and sweet) went very well with the chocolate.  I agreed with him completely.

We both enjoyed it as a simple and yet satisfying dessert.  It was pretty and it was tasty.  When you include how few ingredients it required and how easy it was to prepare, I think it gets very high marks.  

Success!  I would do it again if I can have chocolate in the house that isn't already consumed for being, well, chocolate.  

Be sure to grease the pan!

 

Dried Apricot Cake - A Shaker Recipe

Sometimes when I am thinking about this blog, I just pick a random book off the shelf and browse through it, looking for ideas.  Today I was drawn to The Best of Shaker Cooking, by Amy Bess Miller and Persis Fuller, which was published originally in 1970 and this revised edition in 1985.

ISBN 0-02-584980-8

Shaker cooking is interesting because of the use of herbs and also because those folks really used and polished their recipes.  Cooking tasty, nutritious food was a noble goal in their eyes, as evidenced by this "Comment on Kitchen Education" from the Shaker Manifesto, published in 1883:

The origin of many of the troubles which afflict mankind may be traced to a disordered stomach. ... Give the stomach good, wholesome food, and it will fill your veins with pure blood; which in turn will give you a healthy brain and drive away the whole brood of manufactured troubles. 

The manifesto quote is on page 434 of the cookbook, and is followed by the authors' "Note on Shaker Cooking."

Shaker cooking is not a collection of recipes but rather an attitude toward food and its preparation.  In Shaker kitchens meals were planned and cooked to satisfy both bodily and, in a sense, spiritual hunger.  The Sisters prepared food as efficiently, nutritiously, and tastily as possible.  ... They knew, too, that meals must "create contentment, joy and satisfaction in those who partake of them."

I look at each recipe as one that is proven and pushed to be its best.

In skimming through it, I realized first that I wanted a dessert (my sweet tooth was speaking loudly to me) and second, I had a bag of dried apricots that needed to be used.  A dried apricot cake seemed to fit the requirements.  This recipe had the added bonus that it required sour cream (which I had) and not milk (which I didn't have).  It is credited to the North Union Shaker Village, Ohio.  You can read more about the history of the village by clicking here.

Shaker Dried Apple (or Apricot) Cake (page 213)

1 cup dried apples (or apricots)

1 cup molasses

2/3 cup sour cream

1 cup sugar

1 egg

1 3/4 cups flour, sifted

2 teaspoons baking soda

1 teaspoon cinnamon

1/2 teaspoon cloves

1/2 teaspoon salt

The apricots were soaked the night before.  Just apricots and water left on the counter.

Soak dried apples in water overnight.  In the morning cut fine and simmer in molasses for 20 minutes.  Cool.  Combine cream, sugar, and egg and beat until smooth.  Combine dry ingredients and sift several times.  Blend both mixtures and beat until smooth.  Add fruit and molasses.  Turn into buttered bread pan and bake in  moderate 350 degree F. oven for 1 hour.  This is a very tasty dessert; the dried apples take on a citron flavor.  Makes 1 cake.

My Notes

Plan ahead of the day you are making this cake because you have to soak the dried fruit overnight.  

I took the drained, soaked apricots and first sliced them thinly, then chopped them until they were small bits.  Some bits were smaller than others.  

I love the ulu knife.

I put them in a pan with the molasses, brought them to a simmer over medium heat, then reduced the heat to low for the 20 minute simmer.  I stirred them occasionally.  

Before cooking

When the 20 minutes was up, I turned off the heat to let them cool.  This was a good time to start preheating the oven, although it took more than an hour to cool the fruit.  This is also a good time to butter the loaf pan.  I put the oven to 325 degrees because I was using a glass loaf pan.

After cooking

For the rest of the recipe, I just followed along through the steps as directed.  Here is the sour cream, sugar, and egg after mixing.

Then, in a separate bowl, I placed the dry ingredients.  It is helpful to have the brown spices because instead of sifting the mix, I whisked it until it looked well mixed, and the brown spices show me that.

Both mixtures blended together nicely.

And then the fruit and molasses mixture went in.

I noticed that the mixture started bubbling right away, so I moved quickly to get the batter into the bread pan.  Since I wasn't sure how much the cake would rise, I was concerned that putting in all the batter into one pan would overflow it, so I grabbed another loaf pan, buttered it, and put the rest of the batter in it.  Both pans were no more than 2/3 full.

After one hour of baking, the loaf pans came out.  I was disappointed to see that both had collapsed in the middle, although poking in a pick told me they were cooked through.

I let them cool for a little while, then pulled the cakes out of their pans and let them finish cooling on a rack.  Having them upside down made them look better, but I don't think Paul Hollywood of the Great British Baking Show would have been fooled by this.

The Verdict

These are dark cakes and the scent of cinnamon and cloves filled the house.  Very nice!

The texture was fine, the crumb was moist and tender, and the fruit came through as little bits of chewy dispersed throughout.  I thought it was interesting that I could not tell they were apricots, as the flavors of the molasses and the spices were dominant. 

It was sweet but not cloyingly so.  The exterior was a little chewy and slightly crisp, which was nice.  Later it was not really crisp but very sticky.  If you don't like cloves, find a substitution because they were very dominant, along with the molasses.  I found that there was a pleasant bitterness, which my guest taster thought was wonderful.  He decided this cake would be perfect with his 80 year old madeira, so I gave him some pieces to take home.

My conclusion was that this cake needed a frosting, so I took some cream cheese and spread it on a piece.  That was good, but what was better was mixing cream cheese with a little powdered sugar and a splash of lemon juice, mixing it until it was smooth, then spreading it on the cake.  

That was excellent.  The frosting added another layer of complexity and also balanced the bitter, sweet, and spice with a creamy texture and a little sour from the lemon juice.

I think this cake would be good with a robust tea or hot coffee.  I also think it might be good with a little finely slivered bits of candied ginger in the batter.  Perhaps replacing the cloves with powdered ginger would be good.  A sprinkling of slivered almonds over the frosting would be pretty and tasty, too.

Success!  The recipe "felt" like a quick bread but some of the techniques (cooking the fruit in molasses, mixing the wet with the dry ingredients thoroughly) were different.  I don't know what I did wrong that made the tops sink in, but it turned out to be no big deal once I turned them over.  It is very reminiscent of a gingerbread, but softer and very moist and tender.

A Digestive Biscuit. Very British!

My guest taster was given a very special bottle of wine:  an 80 year old bottle of Sercial Madeira.  We were told it would go best with cheese, nuts, and digestive biscuits.  I accepted the challenge and found a recipe for the biscuits, all the while wondering why they are called that.

A quick trip to Wikipedia answered my question.  Two Scottish doctors created the biscuit in 1839 with the idea it would help with digestion, because of the supposed antacid properties from the sodium bicarbonate in them.  (Click here for the article.)  It was also pointed out that,

[d]igestive biscuits are frequently eaten with tea or coffee.  Sometimes, the biscuit is dunked into the tea and eaten quickly due to the biscuit's tendency to disintegrate when wet.  Digestive biscuits are one of the top 10 biscuits in the United Kingdom for dunking in tea.  The digestive biscuit is also used as a cracker with cheeses, and is often included in "cracker selection" packets.

I found a recipe in The English Biscuit and Cookie Book by Sonia Allison.  Ms. Allison describes them as "Traditional midmorning and very British biscuits".

ISBN 0-312-25347-8

Digestive Biscuits (page 8)

3/4 cup whole-wheat flour

1/4 cup all-purpose flour

1/2 teaspoon baking powder

1 tablespoon oatmeal

4 tablespoons butter

4 tablespoons brown sugar

3 to 4 tablespoons cold milk

Cold butter, cold whole wheat flour, cold milk

1.  Sift the flours and baking powder into a bowl.   Add the oatmeal.

2.  Rub in the butter.  Add the sugar.  Run the mixture through the fingers to mix well.

3.  Using a fork, stir in the milk to form a stiff paste.

4.  Turn onto a floured surface.  Knead lightly until smooth.  Roll out thinly.

5.  Cut into 12 rounds with a 2 1/2-inch cookie cutter, re-rolling and re-cutting trimmings to make the required number.

6.  Transfer to greased cookie sheets and prick all over with a fork. 

7.  Bake until pale gold, allowing 15 to 18 minutes in an oven preheated to 375 degrees F (190 degrees C).

8.  Cool on a wire rack.  Store in an airtight tin when cold.

My Notes

Start the oven preheating!

When I read over the recipe, it struck me that it is basically a pie crust made with whole- wheat flour and with sugar added.  So I treated it as such.

I measured out the butter first (4 tablespoons is 2 ounces) and put it in the freezer.  It wasn't frozen solid but it was very cold.  

My whole-wheat flour lives in the freezer, so it was used that cold. 

The flours and baking powder well mixed.  Oatmeal waiting for inclusion.

When it came time to rub in the butter, I first grated the butter and then mixed it with my fingers into the very cold flour.  

Grated very cold butter.

The same with the sugar -- I measured it into the flour and butter mixture, then mixed it with my fingers until it was well blended (it was still cold).  

The butter is mixed in.

The brown sugar has been added.

It took 5 tablespoons of milk to get the dough to come together like a pie crust.  Four tablespoons just wasn't damp enough.  

With four tablespoons of milk.

Then I put the dough into a covered bowl to rest in the refrigerator for 15 minutes while I cleaned up and set up for rolling and cutting.

With 5 T of milk and some mixing with my hands.

The recipe says you will end up with 12 biscuits, but I got 20.  

Instead of pricking it all over with a fork, I used my Uzbekistan chekich, a bread stamp with a pretty design made from nails.  Actually, I used both of my chekich to see how the biscuits would turn out.  (My daughter brought them back from her trip to Uzbekistan several years ago.)

The first batch came out golden brown in 15 minutes.  The second batch overcooked a little in 14 minutes.  

Second bread stamp pattern

The Verdict

Crispy!  Slightly sweet, and then nutty from the whole wheat.  Overall sort of bland but not in a bad way.  

I can see them as a backdrop for butter or cheese and to go with tea (what I drink) or coffee (what my guest taster drinks).

We had them with the Madeira along with a white cheddar studded with cranberries and also some almonds.  Delightful!  Eighty year old Madeira is smooth, flavorful, and perfect with the suggested accompaniments.  

There is still some Madeira left so making a second batch of digestive biscuits is a high priority.  

Success!

Melt in Your Mouth Blueberry Cake

In 1999 I visited Mt. Vernon, the home of George Washington.  It was a good year to go as it was the 200th anniversary of his death and the docents had set up special tours to commemorate President Washington's accomplishments.  There was also a "funeral" tour where we read passages of news articles and accounts of the nation's shock when his death was announced.  I felt like I was there in the moment, and was genuinely moved and saddened.  

While there I also purchased The Mount Vernon Cookbook, which is a collection of recipes from the members of the Mount Vernon Ladies' Association.  All the proceeds from the sale went to restoration and preservation of the estate and gardens.  Well worth it!

This is a ladies' group cookbook, and I love them because the women who contribute send over their best recipes.  There are reputations to maintain!  

I was perusing the book the other day and came across this recipe for a blueberry cake.  My notes said I had made it in July of 2001, and I had added, "This is incredible.  Wonderful.  Wow."  My thought was that it had been much too long since I had made it!  It needed to be documented in my blog.

It is in the dessert section, but to me, blueberry cake just shouts that it is a coffee cake and could be served as part of a brunch.  Don't tell my guest taster that I served cake for breakfast!  

Melt in Your Mouth Blueberry Cake

2 eggs, separated

1 cup sugar

1/4 teaspoon salt

8 tablespoons margarine, softened

1 teaspoon vanilla

1 1/2 cups sifted flour

1 teaspoon baking powder

1/3 cup milk

1 1/2 cups fresh blueberries

Sugar to sprinkle on batter

Beat egg whites until stiff, adding about 1/4 cup of the sugar called for in the receipt.  Set aside.  Cream margarine; add salt and vanilla.  Add remaining sugar gradually.  Add unbeaten egg yolks and beat until mixture is light and creamy.  Sift 1 1/4 cups of flour and baking powder together.  Add to creamed mixture alternately with the milk.  Fold in beaten egg whites.  Fold in fresh blueberries, which have been gently shaken in 1/4 cup flour so they won't settle.  Turn into greased 8-inch pan.  Sprinkle granulated sugar on top.  Bake at 350 degrees for 50 to 60 minutes.

My Notes

Start preheating the oven.  Choose your pan -- I used a rectangular pan instead of an 8-inch round.  It was glass, so I lowered the temperature to 325 degrees.

This recipe used a lot of bowls!  At least the way I mixed it; I had to do some planning.  

Also, note that the sugar is divided into 1/4 cup and 3/4 cups, and the flour is divided into 1 1/4 cups and 1/4 cups.  

I chose to use butter instead of margarine.

My notes from 2001 suggested putting a "good layer" of sugar on top of the batter.  I had a vague recollection that it formed a crust that was tasty.

I used the mixer to beat the egg whites.  All the rest of the mixing I did by hand.  The pictures show the sequencing as I worked my way through the steps.  The captions help you see the connections.

Bowl #1:  Whipped egg whites with the sugar.

Bowl #2:  Creamed butter with salt and vanilla.

Creamed butter mixture with the yolks mixed in.  (Bowl #3 held the yolks)

Now the flour and milk have been added.  (Bowl #4 held the sifted flour and baking powder)

The whipped egg whites have been folded in.

Bowl #5:  I love how flour acts as little anchors on the blueberries!

Blueberries have been folded in.  I did not add the excess dusting flour.

Gently spread in the pan.

This looks like a good layer.

It went into the oven for 50 minutes.  I checked it at 40 minutes and it was browning but didn't look cooked enough.  At 50 minutes, it was golden brown and a pick inserted into the middle came out clean.  I let it cool about 15 minutes before cutting and serving.

The Verdict

Beautiful to put on the table for serving!

I called it "coffee cake" and served it with fried eggs, coffee, and juice.  

The blueberries were marvelous:  giant, flavorful, and juicy.  They cooked up beautifully.  They made each bite luscious.  

The cake itself was truly melt in your mouth:  delicate, moist, lightly sweet, with a soft vanilla scent.  It was strong enough to support the berries, and tender enough to be a joy to eat.  The sugar crust was good and added a bit of crunch to whole experience.

My guest taster declared that he was considering adding "gluttony" as a new hobby!  

Yes, it was that good.  We managed to restrain ourselves and not eat the whole thing.  We are looking forward to having it again for breakfast.  

I recommend it highly.  Try it!  Plan your bowls and decide if you want to use a mixer for the batter after using it for the whites.  

You can serve this as a dessert, too!  I think it would be a surprising flavor to give to guests.  Not everyone expects blueberry cake for dessert.

I also think it would be good with raspberries or blackberries or cherries.  If you try them, drop me a note!

Success, again!  Good to know it worked then and now, nearly 20 years later.

P.S.

I have written of two other recipes from this book:

Easy Spoon Bread

Sweet Potato-Apple Souffle