Chocolate Peanut Butter Mousse Cake

1 box chocolate cake mix (plus ingredients for preparing)
8 oz peanut butter cups; coarsely chop half of the chocolates

Peanut Butter Mousse:
8 oz cream cheese, at room temperature
1 cup creamy peanut butter
1 cup powdered sugar
1 cup heavy cream
1 tsp vanilla extract

Chocolate Ganache (recipe below)

Preheat oven to 350°F.

Prepare cake mix batter as directed on box (or use your favorite recipe). Stir the coarsely chopped peanut butter cups into the cake batter (reserve the second half of the peanut butter cups to garnish the top). Pour entire batter into one 10” round cake pan. (This is larger than a standard cake pan. If you want to use a standard sized pan, make 3-4 cupcakes out of the batter then pour the remaining batter into the pan. It will overflow if you use all of the batter in a standard pan). Bake cake for 40-45 minutes, or until center is set. Cool cake in pan for 10 minutes, then invert cake onto a wire rack to cool completely.

Prepare peanut butter mousse: In a large bowl, using an electric mixer, beat cream cheese and peanut butter until smooth. Slowly beat in powdered sugar. In a separate bowl, whip heavy cream and vanilla until stiff peaks form. Gently fold whipped cream into the peanut butter mixture.

Invert cake onto a serving platter. Leaving a 1-inch edge around the top of the cake, use a small, sharp knife to cut out the center of the center of the cake to create a cavity about 1-inch deep. (Don’t worry about removing it all in one piece) Use a spatula to spread about 1/3 of the mousse  into the hollowed-out center of the cake. Break the removed cake into pieces and return to the center of the cake, on top of the mousse. Mound cake pieces slightly at the center of the cake. Spread the remaining mousse over the top and sides of the entire cake. Refrigerate the cake until the mousse is firm, about 30 minutes.

Meanwhile, prepare ganache. Allow ganache to cool until thickened but still pourable. Carefully spread the ganache over the top and sides of the cake. Cut remaining peanut butter cups into 1/2” pieces. Scatter over the top of the cake while the ganache is still soft. Refrigerate cake for 1-2 hours before serving.

Chocolate Ganache Frosting

8 oz bittersweet or semisweet chocolate, chopped into small pieces
1 cup heavy cream
1 tsp vanilla extract

Place chopped chocolate  in a mixing bowl. In a saucepan, heat cream until it comes to a boil. Pour cream over chocolate in mixing bowl and stir until chocolate is melted and glossy.  Stir in vanilla.

For a glaze:
Cool ganache slightly (until thick enough that it won’t run off of the cake, but warm enough that it will still drizzle). Pour ganache over cake, starting in the center of the cake, allowing it to drip down the sides.

For a cake frosting, or for piping:
The longer you allow the ganache to cool, the thicker it will set.   For piping or for a regular cake frosting, allow the ganache to completely cool and set up at room temperature. Mix with a whisk slightly just before frosting the cake.

For a whipped filling or frosting:
For a thicker, fluffy frosting, or filling for a cake, chill the ganache in the refrigerator until slightly cold, then whip with a mixer until light and fluffy.

Recipe adapted from Chocolate Cakes

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