Chocolate Brownie Mousse Cake

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This Chocolate Brownie Mousse Cake has layers of fudgy brownie, chocolate mousse and chocolate ganache topped with chocolate whipped cream!

This Chocolate Brownie Mousse Cake was inspired by the Noi Sirius Icelandic Chocolate the that I received in the “Cocoa Loco” February 2025 box from Fikabröd Box. It’s no secret that I love all things chocolate, so I was thrilled to receive this month’s chocolate themed box!

This decadent cake has 4 different chocolate components: a thick fudgy brownie topped with a layer of light and airy chocolate mousse covered in silky smooth chocolate ganache and swirls of homemade chocolate whipped cream. It is truly a chocolate lover’s dream come true!

Looking for more chocolate recipes? Try my Triple Chocolate Cupcakes, Chocolate Sprinkle Cookies, Double Chocolate Muffins or Chocolate Angel Food Cupcakes!

Ingredient Breakdown

Brownie Layer:

Granulated sugar and brown sugar – both sugars are necessary for sweetness and texture.

Vegetable oil – provides texture and moisture.

Butter – provides flavor and texture. I always recommend using unsalted butter but salted butter works if that’s all you have on hand, just be sure to omit the 1/4 teaspoon of salt.

Cocoa powder – gives the brownies their chocolate flavor! I always use natural unsweetened cocoa powder.

Eggs – binds the ingredients and provides structure.

Vanilla extract and salt – enhances flavor. Always use pure vanilla extract instead of imitation for best flavor.

All-purpose flour – just a bit of flour gives the brownies structure while still keeping them fudgy.

Chocolate Mousse:

Heavy cream – gets whipped to soft peaks to make the mousse light and fluffy.

Gelatin leaves – helps set the mousse. I used silver grade gelatin leaves.

Semi-sweet chocolate – I used Noi Sirius Icelandic Chocolate but you can use any brand you prefer!

Egg yolks, granulated sugar and water – this mousse is made using a pâte à bombe base which is whipped egg yolks combined with a sugar syrup that has been cooked to 235°F. This method creates a very light and airy mousse.

How To Make Chocolate Brownie Mousse Cake

1. Make the Brownie Layer: Whisk the granulated sugar, vegetable oil, butter, brown sugar and cocoa powder in a small pot over low heat. Remove from heat once the butter is melted and the mixture is smooth.

2. Whisk in the eggs, vanilla extract and salt until well combined.

3. Fold in the all-purpose flour just almost combined. Pour the batter into the prepared pan.

4. Bake in a 9-inch cake pan at 350°F for 20-25 minutes or until the center is just set. Cool to room temperature then transfer to a 9-inch springform pan with parchment paper lining the sides (this will make it easier to unmold the cake later).

5. Make the Chocolate Mousse: place your mixing bowl and whisk attachment in the fridge for at least 10 minutes. Then, use a hand mixer or a stand mixer fitted with the whisk attachment to whip the heavy cream medium high until soft peaks form. Transfer to the fridge.

6. Soak the gelatin leaves in a bowl of cold water. Set aside.

7. Melt the chocolate and water (60g) over a double boiler on low heat. Whisk until smooth then set aside.

8. Use a stand mixer fitted with the whisk attachment to whip the egg yolks until thickened and pale yellow (about 10 minutes).

9. While the egg yolks are whipping, combine the sugar and water (30g) in small pot. Cook over medium heat until it reaches 235°F. Slowly stream the the sugar syrup into the whipping egg yolks.

10. Squeeze the water out of the gelatin then place in a bowl over a double boiler. Melt over low heat then pour into the whipping egg yolks.

11. Add the melted chocolate to the whipping egg yolks. Continue whipping until cool then fold the whipped cream into the chocolate mixture.

12. Evenly spread the chocolate mousse on top of the cooled brownie in the prepared springform pan. Transfer to the fridge to set for at least 6 hours or overnight.

13. Make the Chocolate Ganache: once the mousse has set, place chocolate in a heat proof bowl. Heat the heavy cream in the microwave or in a small pot over medium heat until it just begins to simmer. Pour the heavy cream over the chocolate then let sit for 2 minutes. Slowly whisk together until combined then pour the ganache on top of the cake. Return to the fridge for at least 30 minutes or until the chocolate ganache has set.

14. Make the Chocolate Whipped Cream:  place your mixing bowl and whisk attachment in the fridge for at least 10 minutes. Use a hand mixer or a stand mixer fitted with the whisk attachment to whip the heavy cream, confectioners’ sugar and cocoa powder on medium high until stiff peaks form. Be careful not to over whip or the texture will be grainy. Use to decorate cake as desired. Store Chocolate Brownie Mousse Cake covered for up to 4 days in the fridge.

Pro Tips For Chocolate Brownie Mousse Cake

• Weigh your ingredients using a kitchen scale! Measuring ingredients by volume is not accurate; baking is a science after all!
• Don’t be tempted to over bake the brownies. They will still be a little gooey when you remove them from the oven but they’ll continue to bake as they cool.
• Use a metal pan to bake the brownies! Glass pans retain heat for longer resulting in unevenly baked brownies.
• Make sure the brownie layer is COMPLETELY COOLED before topping with the chocolate mousse otherwise it melt.

Frequently Asked Questions

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Can This Cake Be Frozen?

Yes! This mousse cake can be frozen for up to 2 months wrapped tightly in plastic wrap. Thaw in the fridge overnight.

Can This Chocolate Brownie Mousse Cake Be Made Gluten Free?

Yes! To make this mousse cake gluten free, simply swap out the all-purpose flour in the brownie layer for your favorite gluten free 1:1 baking flour. The rest of the ingredients in this recipe are already gluten free.

If you try this recipe then please leave a rating/comment below to let me know how you liked it and feel free to ask any recipe questions you may have! 🙂