Triple Chocolate Mousse Cake

Triple Chocolate Mousse Cake is the perfect light dessert recipe. It’s made with a chocolate cake base, cool creamy mousse filling, and topped with rich dark chocolate ganache.

Triple Chocolate Mousse Cake

Ingredients
For the cake
  1. 3 ounces unsweetened chocolate, finely chopped
  2. 1/4 cup hot water
  3. 1 teaspoon instant coffee granules
  4. 2 tablespoons unsweetened Dutch-processed cocoa powder
  5. 3/4 cup granulated sugar
  6. 6 tablespoons unsalted butter, softened
  7. 2 large eggs
  8. 2 large egg yolks
  9. 1 teaspoon vanilla extract
  10. 3/4 cup all-purpose flour
  11. 3/4 teaspoon baking soda
  12. 1/2 teaspoon salt
  13. 1/2 cup buttermilk

For the mousse
  1. 3/4 teaspoon gelatin powder
  2. 1 tablespoon water
  3. 6 ounces semisweet chocolate, coarsely chopped
  4. 2 tablespoons granulated sugar
  5. 1 and 1/2 cups cold heavy cream

For the ganache
  1. 3/4 cups heavy cream
  2. 1 tablespoon unsalted butter
  3. 9 ounces semisweet chocolate, coarsely chopped

Instructions
Make the cake:
  • Adjust the oven rack to the middle of the oven and heat to 350ºF. Lightly grease and flour 1 8-inch springform pan. Tap out any excess flour.
  • Place the chocolate in a small heatproof bowl. Bring water to a boil and pour it over the chocolate. Stir with a silicone spatula until the chocolate is melted and smooth, about 2 minutes. Stir in the coffee granules and cocoa powder. (The chocolate will begin to look more like a paste at this point.) Add 1/4 cup of the sugar and stir until thick and glossy, about 2 minutes.
  • In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and remaining sugar together until light and fluffy. Beat in the eggs and egg yolks, one at a time, mixing well after each addition. Beat in the vanilla. Add the chocolate mixture and mix until thoroughly combined.
  • In a small bowl, combine the flour, baking soda, and salt. Stir with a whisk. Add half of the flour mixture to the chocolate mixture, followed by the buttermilk, mixing until incorporated. Add remaining flour mixture and mix until the batter is thoroughly combined.
  • Spread the batter into the bottom of the prepared pan, smoothing it to the edges with a spatula. Bake for 25 to 30 minutes or until a toothpick inserted into the center comes out clean. Cool to room temperature in the pan on a wire rack.
Make the mousse:
  • In a small bowl, sprinkle the gelatin over water, let stand for 5 minutes. Place chocolate and sugar in a medium bowl. Bring 1/2 cup of the cream to a simmer in a small saucepan over medium-high heat. 
  • Remove from heat; add the softened gelatin and stir until fully dissolved. Pour the cream over the chocolate and whisk until chocolate is melted and the mixture is smooth. Cool to room temperature, stirring occasionally. The mixture will thicken slightly.
  • In the bowl of a stand mixer fitted with the whisk attachment, whip the remaining 1 cup cream at medium speed until it begins to thicken, about 30 seconds. Increase the speed to high and whip until soft peaks form, about 30 to 60 seconds.
  • Use a whisk to mix in 1/3 of the whipped cream into the chocolate mixture. Use a rubber spatula to fold the remaining whipped cream into the chocolate mixture until no streaks appear. 
  • Spoon the chocolate mousse into the pan over the chocolate cake. Smooth the top with an offset spatula. Return the cake to the refrigerator and chill until set, about 2 hours.