Chocolate Peanut Butter Cake with Mascarpone Frosting and Brittle

Adapted from Epicurious and the New York Times

Nut Brittle

1 ½ cups roasted and salted peanuts

½ cup roasted and salted peanuts, finely chopped

1 cup bittersweet chocolate chips

¾ cup water

2 cups white sugar

1 cup light corn syrup

½ teaspoon kosher salt

2 tablespoons unsalted butter

1 teaspoon baking soda

1 teaspoon pure vanilla extract

1.  Line a baking pan with foil and set aside.  Stir together water, white sugar and light corn syrup together in a heavy-bottomed saucepan over medium-high heat.  After sugar has dissolved, stop stirring and bring to a boil, occasionally swirling the pan.  Boil until the mixture has become a deep golden in color, about 10-15 minutes.  Remove from heat and add the salt and butter, whisking continuously.  Be careful, the mixture will bubble vigorously.  Quickly whisk in the 1 ½ whole peanuts, followed by the baking soda and vanilla.

2.  Spread the hot mixture immediately onto the foil, pushing the brittle to the edges of the pan to create an even layer.  Sprinkle the brittle with the chocolate chips and let stand 2 minutes, allowing the candy to melt the chocolate, spread the chocolate as best as you can before topping with the remaining ½ cup finely chopped peanuts.  Bread half the brittle into very small chunks, and the remaining half into larger chunks, about an inch to two inches in width.

Begin preparing the filling several hours ahead.

Filling

2 cups heavy whipping cream

½ cup dark brown sugar, packed

12 oz. bittersweet chocolate, finely chopped

½ cup old-fashioned (natural) smooth peanut butter

1.  Bring cream and sugar to a simmer in a saucepan, whisking to dissolve the sugar.  Remove from heat and set aside.  Add the chocolate and let stand 3 minutes.  Add the peanut butter and whisk until smooth.  Let stand uncovered until firm.

Cake

2 ½ cups all-purpose flour

1 tsp baking powder

1 tsp baking soda

½ tsp kosher salt

10 tablespoons (1 ¼ sticks) unsalted butter, room temperature

½ cup old-fashioned (natural) smooth peanut butter

1 pound dark brown sugar

4 large eggs

1 tsp pure vanilla extract

1 cup buttermilk

1.  Preheat oven to 350 degrees Fahrenheit.  Butter three 9-inch cake pans.  Line bottoms with parchment paper.  Combine first four ingredients together in large bowl.  Using an electric mixer, beat butter, peanut butter, and brown sugar together until light and fluffy, about four minutes.  Add the eggs one at a time, beating after each addition.  Stir in the vanilla.  At low speed, beat in the flour in four additions, alternating with a bit of the buttermilk between each addition.

2.  Divide that batter among the pans and spread evenly.  Bake cakes until tester inserted into center comes out clean, about 25 minutes.  Cool cakes 20 minutes in the pan and then turn out onto cooling racks, peeling off the parchment paper, until completely cooled.

Frosting

1 8oz. container of mascarpone cheese

2 tablespoons unsalted butter

2 cups heavy whipping cream

¾ cups white sugar

1 teaspoon pure vanilla extract

1.  Beat together the mascarpone cheese, butter and ¼ cup of the white sugar until light and fluffy, about three minutes.  In a separate bowl, beat the whipping cream, the remaining sugar and the vanilla until you have a stiff whipped cream.  Beat in the mascarpone mixture in two additions, beating the frosting fully after each addition.  Frost immediately.

Assembly

1.  Using a serrated knife, carefully level the cakes and cut each cake in half creating six layers.  Place a bottom layer on a cake round and spread with one-fifth of the chocolate ganache filling and about ¼ cup of the finely chopped brittle.  Top with an inverted top layer and spread again with one-fifth of the filling and another ¼ cup of the finely chopped brittle.  Repeat until all six layers are stacked and filled.  Refrigerate for one hour before frosting so that the cakes have time to set.

2.  Make the frosting at this point.  Frost the outside of the cake.  Top the cake with the larger chunks.  Keep refrigerated for up to four days.  Bring slices to room temperature before serving.

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