A rich and fudgy brownie bottom with an easy but decadent and eggless chocolate mousse on top. This chocolate brownie mousse cake utilizes a boxed brownie mix to make this yummy dessert come together even quicker!

chocolate brownie mousse cake slice on plate

I had a craving for some serious chocolate and thought up this chocolate brownie mousse cake to satisfy that craving. I wanted a fairly no fuss dessert. While mousse isn't always no fuss, as it can involve cooking eggs and sugar to a certain temperature before adding in beaten egg whites or whipped cream, this version is! I'm also subbing in a boxed brownie mix for the base layer of the cake because let's be honest, boxed brownies are pretty delicious.

What is mousse?

Mousse typically consists of 4 parts, a base, a binder, an aerator and any add-ins/flavorings. For this mousse, the base will be melted bittersweet chocolate. There is no binder in this mousse recipe because the chocolate will act as the binder, thickening the mousse as it cools. Another binder most typically used in mousse is gelatin but again, this mousse will set up without it. For the aerator, heavy whipping cream is used. This will give the mousse its signature light and fluffy texture and without having to use any raw eggs, so it's pregnant mama safe :-). A little salt and vanilla get added in for that last component of flavorings.

How to make the cake

To start this recipe, prepare your boxed brownie mix according to the package directions. A 9 inch springform pan is used to layer the brownie and chocolate mousse. Bake the brownie according to the time needed to bake a 9 x 9 pan of brownies.

Next you will prepare the mousse. Start by finely chopping the bittersweet chocolate. Then heat a cup of the heavy cream. I like to just microwave the cream for about 2 minutes but you could also use the stovetop for this as well. Pour the hot cream over the chocolate and stir until it is completely melted. Add the salt and vanilla and stir to combine. Let the chocolate cool for about 10 minutes before folding in the whipped cream.

In a stand mixer or using a hand mixer, beat the remaining heavy cream with some sugar until soft to medium peaks form. You don't want to beat it to stiff peaks as it could cause the mousse to turn grainy. Add about half a cup of the whipped cream to the chocolate, stirring to lighten it up. Then add the rest of the whipped cream, folding it gently until completely incorporated.

Pour the mousse over the baked and cooled brownie and cover and chill the cake at least 6 hours or preferably overnight. I garnished the top of the cake with more lightly sweetened whipped cream for some contrast with the chocolate.

chocolate brownie mousse cake on a cake pedestal

How to store the cake

This chocolate brownie mousse cake needs to be kept refrigerated until serving. For any leftovers, keep them covered in the refrigerator. The cake should last 3-4 days in the refrigerator.

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Tag me on Instagram @themarblekitchenblog if you make this and leave a star rating and comment below! Thank you and enjoy!