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Chocolate cake on a blue cake stand with plates next to it.

Rocky Road Cake

5 from 1 vote
Rich, dark chocolate cake layers, filled with chocolate ganache, marshmallows, peanuts and toffee bits, covered with a silky chocolate buttercream.

Ingredients

For the Cake

  • 2 cups (240 g) all-purpose flour
  • 1 3/4 cups (350 g) granulated sugar
  • 3/4 cups (88.5 g) good quality dark cocoa powder, I use Extra Brute Cacao Barry
  • 2 teaspoons (8 g) baking soda
  • 3/4 teaspoon (3 g) baking powder
  • 1 teaspoon (6 g) kosher salt
  • 1 cup (240 g) buttermilk, room temperature
  • 1/2 cup (109 g) vegetable oil
  • 3 large eggs, at room temperature
  • 1 teaspoon (4.2 g) pure vanilla extract
  • 1 cup (236.6 g) hot water (or hot coffee)

For the Filling

  • 1 1/2 cups (225 g) semi-sweet chocolate chips
  • 3/4 cup (173.25 g) heavy cream
  • 1 1/2 cup (75 g) mini marshmallows
  • 3/4 cup (112.5 g) chopped peanuts
  • 3/4 cup (112.5 g) toffee bits

For the Buttercream

  • 2 cups (452 g) unsalted butter, slightly cold
  • 10 oz. good quality chocolate of your choice, I use dark or semi, melted and cooled
  • 5 cups (625 g) powdered sugar, measured and then sifted
  • 2 teaspoons (8.4 g) pure vanilla extract
  • Pinch of salt
  • 1/4 cup (57.7 g) heavy cream
  • *This buttercream recipe makes enough to fill and cover your cake. If you want to add additional piping you’ll want to make an extra 1/4 batch.

Instructions

For the Cake

  • Preheat the oven to 325 degrees F. Spray three 8-inch round cake pans with nonstick spray. Line the bottom of each pan with parchment paper, then spray the parchment paper. Set aside.
  • In a medium size mixing bowl, whisk together the flour, sugar, cocoa, baking soda, baking powder, and salt. Set aside.
  • In another bowl, combine the buttermilk, oil, eggs, water (or coffee) and vanilla. Whisk until combined.
  • With the mixer on low speed, slowly add the wet ingredients to the dry, scraping the bottom of the bowl with a rubber spatula.
  • Evenly divide the batter into each of the three pans (about 15 to 16 ounces of batter in each 8-inch pan). Bake for 23 to 28 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs on it.
  • Cool in the pans for 10 minutes, then turn them out onto a cooling rack and cool completely. (I like to spray my cooling racks with nonstick spray to ensure non of the cake sticks to the racks).
  • If needed, level your cake layers to ensure a completely even surface for frosting and stacking. After leveling you can wrap each cake layer in plastic wrap and freeze until ready to use.

For the Filling

  • Heat the cream in a microwave safe bowl for about one to two minutes. Pour the heated cream over the chocolate chips in a medium sized bowl. Let sit for about five minutes.
  • Stir the chocolate and cream until nice and smooth. Add the marshmallows, peanuts and toffee bits and stir until combined.
  • Let the filling cool before using.
    If you make the filling ahead of time, you will want to heat it up slightly to make it spreadable again.

For the Buttercream

  • In a microwave safe bowl, heat the chocolate chips and heavy cream for about 40 to 60 seconds. Stir until smooth. Let cool slightly.
  • In a bowl fitted with a paddle attachment, beat the butter on medium speed for about two minutes.
  • With the mixer on low speed, slowly add the chocolate ganache and stir until smooth. Gradually add the powdered sugar and mix until combined.
  • Add the vanilla and salt. Turn the mixer to medium-high and beat the buttercream for another 3-4 minutes until light and fluffy. 
  • Before frosting your cake, use a wooden spoon to hand mix the frosting to push out air bubbles.

Assembly

  • Place the first cake layer on a cake board or cake plate, top side up.
  • Pipe a rim of frosting around the edge of cake layer before adding the filling. This creates a nice barrier so the filling stays in place.
  • Spread half of the filling within the frosting barrier. 
  • Place the second cake layer on top and repeat steps 2 and 3.
  • Place your final cake layer, top side down, on top of the filling. Spread a thin layer of buttercream around the entire cake. This is the crumb coat and will help lock crumbs into place. Freeze for about 10 minutes to set the crumb coat.
  • Continue to frost the cake with the remainder of the chocolate buttercream, saving about a half cup of buttercream to do the design show above.
Course: Dessert
Cuisine: Cake
Keyword: chocolate buttercream, Chocolate Cake, Rocky Road, Rocky Road Cake