Sweet Potato Spice Cake with Brown Sugar Buttercream

I could not get this cake out of my mind when I first saw this recipe.  I knew I had to try it and I immediately added it to my Thanksgiving Day menu.  We hosted Thanksgiving this year with Ryan’s family at our place.  I made this cake the night before but I would recommend making the filling and buttercream ahead of time if possible.  This cake is very intensive and takes a long time because of all the steps – so if you make it I would recommend making it for a special occasion or a day when you have a good chunk of time to spend on it.   It turned out great though and everyone liked it!  My favorite part was the marshmallow filling and the brown sugar buttercream.  I absolutely loved watching the marshmallows turn a delightful golden brown as they toasted in the oven right before my eyes.  It was like a campfire in my kitchen…minus the flames.  I really want to incorporate the marshmallow filling into other desserts and cakes! 

Sweet Potato Spice Cake with Brown Sugar Buttercream 

Ingredients

For the Cake Layers:

3 large sweet potatoes

2 cups sugar

4 large eggs, at room temperature

1-1/4 cups canola oil

2 cups cake flour

1 tablespoon ground cinnamon

2 teaspoons baking powder

1 teaspoon salt

1 teaspoon ground nutmeg

1/2 teaspoon ground ginger

2 tablespoons brandy

2 teaspoons pure vanilla extract

3/4 cup crystallized ginger, chopped

For the Filling:

16 large white marshmallows

1 cup powdered sugar

1 cup butter (2 sticks), at room temperature

1/2 teaspoon pure vanilla extract

1 jar marshmallow cream (such as Marshmallow Fluff)

For the Buttercream:

5 large egg whites

1-1/4 cups light brown sugar

1-1/2 cups (3 sticks) unsalted butter, softened and cut into cubes

2 teaspoons pure vanilla extract

pinch of salt

a few pinches of cinnamon, to taste

For the Candied Pecans:

2 tablespoons unsalted butter

2 tablespoons brown sugar

1 cup pecan pieces

Instructions

For the Cake Layers:

Preheat oven to 350°F. Grease two 9-inch round cake pans, dust with flour, tap out excess and set aside.

Place the sweet potatoes on a microwave-safe plate and pierce them with a fork. Microwave until they are tender (about 7-8 minutes each side). Carefully remove the skin when cool enough to touch, and mash the flesh into a coarse puree.

In a large bowl beat the sugar and eggs together with an electric mixer on medium-high speed until light and fluffy, about 5 minutes. Add the oil and beat on medium until combined. Add the cooled sweet potato puree and mix until combined.

Sift dry ingredients together (cake flour, cinnamon, baking powder, salt, nutmeg and ground ginger) and then add to sweet potato mixture.

Mix in brandy and vanilla. Gently stir in crystallized ginger.

Evenly distribute batter into the prepared pans, smooth tops and place in the center of the middle rack of the oven, about 2 inches apart. Bake until a knife or skewer inserted into the center comes out clean, about 40 minutes.

Let pans cool on a wire rack 10 minutes. Invert cakes onto rack and cool them completely.

For the Filling:

Place marshmallows on cookie sheet lined with parchment paper and sprayed with nonstick cooking spray. Place on lower rack of oven, and broil marshmallows until nice and brown on top, between 30-60 seconds. Remove pan from oven and gently turn the marshmallows over, and broil until they are golden brown.

In bowl with an electric mixer, combine butter and icing sugar on low until blended, about 1 minute. Add vanilla and mix on med-high for about 3 minutes.

Add marshmallow cream and toasted marshmallows, and mix on lowest setting for about 1 minute.

For the Buttercream:

In a large bowl, add egg whites and sugar, and simmer over a pot of water (not boiling), whisking constantly but gently, until temperature reaches 160°F, or if you don't have a candy thermometer, until the sugar has completely dissolved and the egg whites are hot.

With whisk attachment of mixer, begin to whip until the meringue is thick, glossy, and the bottom of the bowl feels neutral to the touch (this can take up to 10 minutes or so). *Don't begin adding butter until the bottom of the bowl feels neutral, and not warm.

With mixer on low speed, add butter cubes, one at a time, until incorporated, and mix until it has reached a silky smooth texture (if curdles, keep mixing and it will come back to smooth). *If mixture is too runny, refrigerate for about 15 minutes and continue mixing with paddle attachment until it comes together. Add vanilla and salt, continuing to beat on low speed until well combined. Add cinnamon to taste and blend.

For the Candied Pecans:

Melt the butter in a small pan. Mix in brown sugar, and add the pecans. Toss to coat.

Cook on medium low heat for about 15 minutes, stirring occasionally. Be sure to watch carefully so they don’t burn.

Turn out onto parchment paper or aluminum foil and let cool for 5 minutes; break apart into smaller pieces if using halves.

Assembly of the Autumn Delight Cake

Slice both cake layers in half horizontally, so you have 4 cake layers.

Place the first layer on a plate, pedestal or cake board cut side up (so bottom of the cake layer is touching plate), and spread ~3/4 cup of Toasted Marshmallow Filling with a small offset palette knife, leaving 1" or so around the edge. Sprinkle with a handful of candied pecans pieces.

Repeat previous step until you get to the final cake layer. Place last layer face down and chill cake for 30-40 minutes.

Frost cake with Brown Sugar Buttercream and top with a generous handful of candied pecans and crystallized ginger.

Finished cake can be kept at room temperature for up to 8 hours. Keep refrigerated if longer than 8 hours, but always serve at room temperature (Swiss Buttercream should never be served cold, as it goes back to a cold-butter texture).

Recipe adapted from Sweetapolita