Brownie Blackout Mousse Cake
Prep time
Cook time
Total time
This is the ULTIMATE chocolate lover's dream cake. Mike never gets chocolate, so I decided to give him ALL THE CHOCOLATE at once! This cake is the perfect balance of sweetness, and it is super rich as you might expect! It tastes best when made a day in advance and allowed to meld in the fridge overnight. Pour a big ol' glass of milk and dig in.
Serves: 20
Brownie Layer Ingredients:
  • 2 boxes brownie mix (plus ingredients needed to prepare it)
Pudding Ingredients:
  • 1 1/4 cups water plus 1/4 cup water, separated
  • 1 1/4 cups granulated sugar
  • 1 1/2 teaspoons honey
  • 1/2 cup unsweetened cocoa powder
  • a scant 1/3 cup cornstarch
  • a little less than 3 tablespoons unsalted Plugrá butter, cold and cut into 1-inch cubes
  • 1/4 teaspoon pure vanilla extract
Mousse Ingredients:
  • 1 cup heavy cream
  • 8 ounces bittersweet chocolate, finely chopped
  • 3 eggs
  • 3/4 cup granulated sugar
  • 2 tablespoons water
  • 1 tablespoon vanilla extract
  • 8 tablespoons unsalted Plugrá butter, at room temperature, cut into 1/2-inch pieces
Topping Ingredients:
  • 1 cup heavy whipping cream
  • 1/2 teaspoon gelatin
  • 2 tablespoons cold water
  • 3 tablespoons powdered sugar
  1. Prepare the brownie layers: Prepare two 9-inch springform pans with a parchment paper round in the bottom each. Spray the pans with cooking spray. Prepare the brownie batter according to the package directions and bake it in the springform pans for about 30 minutes (brownies look underdone when they're ready, so be careful not to overbake. My package said to bake them 39 minutes but they were ready at 30). Allow to cool completely and then open the springform and lift the layers from the parchment to ensure they will come unstuck easily later. Close the springform again (with layers still sitting inside but loosened now) and set aside.
  2. Make the pudding: Bring the 1 1/4 cups of the water, sugar, honey and cocoa powder to a boil in a large saucepan over medium-high heat, whisking occasionally. In a separate small bowl, whisk the remaining 1/4 cup of water and the cornstarch together until smooth. Whisk the corn starch mixture into the cocoa mixture and bring it to a boil, whisking constantly. Cook, whisking constantly, until very thick, 3 to 4 minutes. Remove the mixture from the heat and stir in the butter and vanilla extract. Pour the pudding into a separate, shallow bowl. Cover with plastic wrap pressed right to the surface (to prevent it from forming a skin) and chill it in the fridge until firm, about 45 minutes.
  3. Begin assembly: Spread half the pudding over one brownie layer inside its springform pan (this is the pan you'll build your whole cake in). Remove the other brownie layer from its springform pan entirely and place it on top of the pudding layer. Top it with the rest of the pudding and smooth it into an even layer. Set this in the fridge to chill.
  4. Make the filling: Melt chocolate by heating on half power for 30 second intervals, stirring after each, until it's smooth. Transfer it to a shallow dish and allow it to cool completely. In a chilled bowl, beat the heavy whipping cream to stiff peaks. Place it in a bowl in the fridge to chill until it’s needed. In the heatproof bowl of a stand mixer, beat together eggs, sugar, and water for 5 minutes until pale yellow and slightly thickened. Set the bowl over a saucepan of simmering water to form a sort of double boiler. Heat, whisking occasionally, until a candy thermometer reads 160 degrees F.
  5. Put the bowl onto the stand mixer carefully and beat on medium speed until cooled to room temperature and thickened, about 8 minutes. While beating, add in the chocolate and vanilla. If your chocolate seems to stick to the bowl and get difficult here, just turn the mixer up for a few seconds and all will be well. Beat in the room temperature butter a piece at a time, mixing between each. Fold in the whipped cream until no white streaks remain, and then pour the mixture over your last pudding layer. Cover and chill for at least 3 hours or overnight.
  6. Make the topping: In a small bowl, sprinkle the gelatin over the 2 tablespoons cold water to soften for 2 minutes. Heat for 15 or so seconds in the microwave, whisking to dissolve the gelatin. Whip 1 cup heavy whipping cream to stiff peaks, adding the gelatin and powdered sugar halfway through. Gently spread the whipped cream over your mousse layer and chill in the fridge until set. Slice your cake and serve!
Recipe by Willow Bird Baking at