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side view of a slice of mousse cake next to a fork on a plate.

Triple Chocolate Brownie Mousse Cake

5 Stars 4 Stars 3 Stars 2 Stars 1 Star 5 from 7 reviews
  • Author: Julianne Dell
  • Prep Time: 1 hour
  • Chill Time: 6 hours
  • Total Time: 7 hours
  • Yield: 10-12 slices
  • Category: Dessert
  • Method: Oven
  • Cuisine: American

Description

The mouthwatering Triple Chocolate Brownie Mousse Cake is so sinful. There’s a fudgy brownie on the bottom, a layer of easy chocolate mousse and finally a layer of mouthwatering brownie batter mousse.


Ingredients

For the Brownie Layer

  • 1 box (19oz) fudgy chocolate brownie mix 
  • Ingredients listed on the box: oil, eggs, water

For the Chocolate Mousse

  • 1 tablespoon (15ml) water
  • 1 teaspoon gelatin
  • ½ cup (90g) semi-sweet chocolate chips
  • 1 cup plus 4 tablespoons (295ml) heavy whipping cream, divided
  • ½ cup (65g) powdered sugar
  • 8oz (226g) cream cheese, at room temperature
  • ¼ cup (48g) granulated sugar
  • 2 tablespoons (10g) cocoa powder
  • 1 teaspoon (5ml) vanilla extract

For the Brownie Mousse

  • 1 tablespoon (15ml) cold water
  • 1 teaspoon gelatin
  • 1 ½ cups (354ml) heavy whipping cream
  • ¾ cup dry brownie mix
  • 1 cup chopped brownies (store-bought)

For the Toppings

  • ½ cup (90g) dark or semi-sweet chocolate chips
  • ¾ cup + 2 tablespoons (207ml) heavy whipping cream, divided
  • 3 tablespoons (24g) powdered sugar
  • Additional chopped brownie for garnish (optional)

Instructions

For the Brownie Layer

  1. Preheat the oven to 350°F. Line the bottom of a 9-inch springform pan with parchment paper.
  2. In a medium-sized bowl, combine the brownie mix, with the ingredients listed on the box. Stir until the batter is well combined and there are no dry ingredients left.
  3. Pour the batter into the springform pan and spread evenly. Bake at 350°F for 35-40 minutes until the center is baked but still slightly fudgy. Allow the brownie to cool completely.

For the Chocolate Mousse

  1. In a small dish, combine 1 tablespoon of cold water with 1 teaspoon gelatin. Sprinkle the gelatin over the cold water and allow it to set to a solid (2-3 minutes). 
  2. In a microwave-safe bowl, combine the chocolate chips and 2 tablespoons of heavy whipping cream. Microwave in 30-second increments, stirring each time until the chocolate is melted and smooth.
  3. Next, melt the gelatin in the microwave for 5-8 seconds until it turns back into a liquid. Watch it closely! Remove any lumps that did not melt.  Stir the liquid gelatin into the melted chocolate and set it aside to cool.
  4. Prepare the whipping cream. Chill a mixing bowl in the freezer for 5 minutes. Using the chilled bowl, beat 1 cup of heavy cream on high speed until it’s thickened to soft peaks. Next, add the powdered sugar and continue beating at high speed until stiff peaks form. Set the whipped cream aside.
  5. Combine together the cream cheese and sugar, beating at a medium-high speed for 2-3 minutes, until the cream cheese is completely smooth, scraping the bowl occasionally. Next, add the cocoa powder and beat until well combined, scraping down the bowl as needed.
  6. Next, slowly add 2 tablespoons of heavy whipping cream and the vanilla extract and continue beating until combined. Then add the melted chocolate and mix thoroughly into the cream cheese mixture. Finally, fold the prepared whipped cream into the cream cheese and stir gently until the mixture is well combined.
  7. Place the cooled brownie in the bottom of the springform pan lined with parchment paper. It’s helpful to line the sides with parchment paper or a cake collar. Pour the chocolate mouse over top of the cooled brownie and refrigerate while you prepare the next layer.

For the Brownie Mousse

  1. Prepare the heat-treated brownie mix. Bake the brownie mix on a baking sheet lined with parchment paper at 350°F for 8-10 minutes until it reaches 160 degrees F, stirring halfway in between. Allow the mixture to cool and then sift with a mesh sieve. 
  2. In a small dish, combine 1 tablespoon of cold water with 1 teaspoon of gelatin. Sprinkle the gelatin over the cold water and allow it to set to a solid (2-3 minutes). Next, melt the solid gelatin in the microwave for 8-10 seconds until it turns back to a liquid. Watch it closely!
  3. Prepare the whipping cream. Using a chilled bowl, beat 1 cup of heavy cream on high speed until it’s thickened to soft peaks. Next, add the brownie mix and liquid gelatin and continue beating at high speed until stiff peaks form. Set the whipped cream aside.
  4. Chop 1 cup of the prepared brownies into small pieces, about the size of a dime or smaller and gently fold them into the brownie batter mousse. Pour the brownie batter mousse over the chocolate mousse.
  5. Refrigerate the cake for 4-6 hours until the mousse layers are set.

For the Toppings

  1. Chocolate ganache: In a microwave-safe dish, combine the chocolate chips with 2 tablespoons heavy whipping cream. Microwave for 30-60 seconds until the chocolate starts to melt. Stir until the chocolate is completely smooth. The chocolate should run smoothly off your spoon. If it is still too thick, add additional heavy whipping cream.
  2. Remove the chilled cake from the pan and use a piping bag or spoon and gently pour the ganache along the edges of the cake. The chocolate will run down the sides. Allow the ganache to set before adding any additional toppings. 
  3. Whipped Cream: Prepare another batch of whipped cream as instruction above using 3/4 cup heavy cream, combined with the powdered sugar. Pipe a border around the outside edge of the cake and garnish with leftover brownies.


Notes

Preparation and Storage:

  • Finished chocolate mousse cake will last covered in the fridge for up to 4 days! Wrap tightly in plastic wrap or put the entire pan in an airtight container. This can be prepared up to 2 days in advance, but I do recommend adding the topping the day of serving if possible. Once the ganache is added, it’s difficult to place back in the pan.
  • Freezing: You could freeze this once it’s been fully prepared and set, but the texture may change once it’s thawed. I recommend freezing it while it’s still in the pan, wrapped tightly with two layers of plastic wrap, plus foil to prevent freezer burn.

For the brownie layers

  • For the bottom layer, consider using this cocoa powder brownie, baked in the springform pan. 
  • A boxed brownie mix works best for the brownie batter mouse
  • Chopped brownies are used in the mousse and for garnish. For this I recommend buying already prepared brownies, or do a double batch of homemade brownies, using the leftovers for the mousse and garnish.