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.
Preheat the oven to 350ºF. Lightly spray the bottom and sides of an 8-inch springform pan with nonstick spray. Line the bottom and sides with parchment paper and lightly spray the paper with nonstick spray
Add the chocolate and butter to a medium saucepan. Warm over medium-low heat, stirring constantly until chocolate is melty and smooth. Whisk in the sugar. Set aside to cool slightly. It can be warm, you just don't want it too hot that it scrambles the eggs.
Once cooled, whisk in the eggs and vanilla until combined.
Sift the flour, cocoa powder, and salt into the chocolate mixture and fold together with a rubber spatula just until no dry streaks of flour are visible. Take care not to overmix.
Spread the batter evenly into the bottom of the prepared pan. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out with only a few moist crumbs.
Leave the brownie in the pan and set it wire rack to cool completely. Or pop it in the refrigerator for 15-20 minutes.
Make the mousse:
In a small bowl, sprinkle the gelatin over the water, let stand for 5 minutes. Place chocolate in a medium bowl. Add 1/2 cup of the cream and 2 tablespoons of sugar to a small saucepan. Bring to a simmer over medium-high heat. Stir to make sure the sugar is dissolved.
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 or with a handheld electric mixer, 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 medium to stiff peaks form, about 30 to 60 seconds.
Use a whisk to mix ⅓ 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.
Spread the mousse evenly over the top of the cooled brownie layer. Refrigerate while you make the ganache.
Make the ganache:
Heat the cream and butter in a medium saucepan over medium-high heat. Remove from heat just before it begins to boil.
Place the chocolate in a medium heatproof bowl and pour the hot cream over the chocolate. Stir until chocolate is melted and smooth. Set aside to cool until the ganache is no longer warm to the touch.
Spread the ganache over the top of the mousse layer and refrigerate until set. About 1 hour.
Remove the sides of the pan and carefully pull the parchment paper off the cake. Transfer the cake to a serving platter and serve with whipped cream or fresh berries.
Notes
This recipe was updated! Everything is the same except for the base layer. I updated the base so it no longer requires melting chocolate with hot water. Too many readers had difficulty with this. You'll still get the same rich chocolate base without all the hassle. The base is from my Nutella Mousse Cake.
If you'd like to make the original cake base, you can find it here -> Original Mousse Cake
Cocoa powder: Dutch-processed has a smoother flavor but natural cocoa can also be used.
Cake pan: If you don't have a springform pan, you can use a regular 8-inch round cake pan that's 3-inches tall. In step 3 of "make the ganache", place the cake in the freezer for 1 hour. Once it's firm enough to unmold, place a sheet of parchment paper over the top then set a cutting board or large plate over the paper. Flip the entire assembly over so the cake can release from the pan. Remove the pan and use the same method to flip the cake upright onto a serving platter.
Serving the cake: The cake slices best when well chilled. Once sliced, allow the slices to sit at room temperature for about 30 minutes. This allows the layers to soften slightly, making the mousse & ganache extra silky.
Make ahead tip
The cake will keep for up to 3 days stored in the refrigerator.
The cake can be frozen for up to 3 months. Thaw in the refrigerator overnight before serving.