Cakes & Cupcakes

Boxed Brownie Mousse Cake

February 5, 2019

A silky smooth, decadent boxed brownie mousse cake is the ultimate chocolate lover’s dessert. A layer of rich chocolate mousse […]

A silky smooth, decadent boxed brownie mousse cake is the ultimate chocolate lover’s dessert. A layer of rich chocolate mousse sandwiched between a thick, fudgy brownie and a cloud of freshly whipped cream. Pure chocolate heaven!

I’m that girl that goes out to dinner and immediately looks at the dessert menu first. (Please tell me I’m not the only one.) I like to know what I’m in for and whether or not there is a little something-something splurge-worthy on the after dinner menu or if I’m better off double dipping in the bread basket. My sweet tooth automatically makes a b-line for all the chocolatey things {shocking, I know}. I leave the tart and fruity mango sorbets and key lime pies to my better half since that’s more his cup of tea. More often than not we end up with his and hers desserts and everyone wins.


A couple of weeks ago we were in NYC and I ordered a rich and decadent chocolate mousse that was seriously something to write home about. It was insanely rich and silky smooth. Served with just a dollop of freshly whipped cream it could not have been more simple but so incredibly delicious at the same time. I knew it had to be good when my husband repeatedly tried to steal a spoonful and the waiter asked if we’d like one more to share. For the record, we declined. {regretfully} My sweet tooth and I haven’t been able to forget that dreamy chocolate mousse and I literally cannot wait to get back to New York just for dessert.


Last weekend I decided to make my own over-the-top chocolate mousse dessert in hopes that it would be half as delicious as the mousse from the authentic little underground Italian place we stumbled upon. So I made a super rich and ultra decadent chocolate mousse from scratch and then it occurred to me it would be even more perfect sandwiched between layers of dark chocolate brownie and fluffy, freshly whipped cream. You know, because I’m extra like that. Not so extra though that the entire dessert had to be made from scratch. I’m all for cutting corners when the time is right and there is no shame in boxed brownie mix people. Not to mention that all that mousse making made for a lot of dishes already and I was over it.


And there you have it. That, my friends, it how the Boxed Brownie Mousse Cake came to be. I mean, one look at this triple layer chocolate dream and I say “pass the fork”. This cake has so many things going for it, number one being that each layer is so easy to whip up and together they make just the right amount of fancy. To make this triple threat cake, start with your favorite box brownie mix. Any brand will do, but go for fudgy. You’ll bake the brownies in a springform pan until slightly under baked. While the brownies cool, you’ll whip up the chocolate mousse until it’s light and airy. After layering the mousse over the brownies, you’ll add a fluffy cloud of freshly whipped cream on top. After some chill time in the fridge simply top with chocolate shavings and dessert is served!


This is just the kind of chocolate lover’s dessert that will win over your hubby, boyfriend, or as my teenagers would say, your boo-thang this Valentine’s Day. February {aka, my favorite foodie month ever} is all about dreamy chocolate desserts like this Boxed Brownie Mousse Cake and I’m all in for this chocolate fest!  If you are in need of another chocolate fix right away, check to these recent posts for my Wanna-Be Brownie Cookies and these super easy, no bake Salted Caramel Dark Chocolate Cups. More of where that came from ahead so don’t go anywhere.

Be sure to sign up on the homepage for weekly recipes straight to your inbox. I hope you’ll give this Boxed Brownie Mousse Cake a try and if you do, be sure to tag @brownedbutterblondie on Instagram so I can see what you are baking up in your kitchen. And follow me on Pinterest for all the latest recipe details. I’ll see you back here next week for another drool-worthy chocolate recipe.

Until then, happy baking!

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Boxed Brownie Mousse Cake

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  • Author: Browned Butter Blondie
  • Prep Time: 60 mins
  • Cook Time: 25 mins
  • Total Time: 1 hour 25 mins
  • Yield: 1 1x
  • Category: Dessert


A silky smooth, decadent boxed brownie mousse cake is the ultimate chocolate lover’s dessert. A layer of rich chocolate mousse sandwiched between a thick, fudgy brownie and a cloud of freshly whipped cream. Pure chocolate heaven!



For the Brownie Layer

  • 1 boxed brownie mix

For the Chocolate Mousse Layer

  • 9 ounces (about 2 1/2 bars) dark chocolate, chopped {I use Valrhona 71% Cacao Dark Chocolate Bar}
  • 1/2 cup plus 2 TBSP heavy whipping cream
  • 4 egg yolks, room temperature
  • 1/4 cup plus 1 TBSP granulated sugar
  • 1/4 cup water
  • 2 egg whites, room temperature
  • 1/8 tsp salt

For the Whipped Cream Layer

  • 1 cup heavy whipping cream
  • 1 TBSP confectioner’s sugar


For the Brownie Layer

  1. Preheat oven to 350 degrees.
  2. Spray a 9 inch springform pan with non-stick cooking spray and line bottom and sides with parchment paper.
  3. Set aside.
  4. Mix a box of brownie mix according to package directions and spread into bottom of the prepared pan.
  5. Bake according to package directions, baking 5 minutes less than instructed.
  6. Remove pan from oven and allow brownies to cool.

For Chocolate Mousse Layer

  1. Whip heavy whipping cream in the stand of an electric mixer fitted with the whisk attachment until light and fluffy. Do not over mix.
  2. Place in refrigerator to keep cool.
  3. Over a double boiler on medium-low heat, melt chopped chocolate, stirring often until smooth and fully melted.
  4. Remove from heat.
  5. In a clean bowl in the stand of an electric mixer, whip egg yolks on high.
  6. Meanwhile, heat water and granulated sugar on high heat in a small saucepan.
  7. Once boiling, very slowly add the sugar/water mixture to the beaten egg yolks in the mixer and continue to beat on high speed.
  8. Mixture will thicken and cool and be pale yellow.
  9. Using large folding motions, mix the melted chocolate into the egg yolk mixture until combined.
  10. In a separate clean bowl of an electric mixer, whip egg whites until foamy but not dry.
  11. Quickly stir 1/3 of the egg white mixture into the chocolate mixture, incorporating completely.
  12. Gradually add the rest of the egg whites using large folding motions.
  13. Remove whipped cream from refrigerator and gently fold into the chocolate mixture until combined.
  14. Spread the mousse onto the top of the cooled brownie, using and offset spatula to level the brownie layer.
  15. Place pan in refrigerator.
  16. Mix 1 cup of heavy whipping cream and 1 TBSP confectioner’s sugar in the stand of an electric mixer with the whisk attachment until smooth but not completely set.
  17. Remove from mixer and continue to mix with a hand held whisk for 30 seconds until whipped and smooth.
  18. Remove mousse from refrigerator and spoon whipped cream on top of the mousse layer, again using a spatula to level the top.
  19. Refrigerate for 4 hours or overnight.
  20. Sprinkle top of cake with chocolate shavings or curls.
  21. Serve cold.


Left over cake can be stored tightly wrapped in refrigerator.
When baking boxed brownies, add 2 TBSP freshly brewed espresso instead of water for a richer, more chocolatey brownie.


  • Reply
    April 27, 2020 at 7:17 pm

    Hello! I don’t have a springform pan. Could I sub another dish? Trying to judge how deep the dish needs to be to accommodate all the layers.

    • Reply
      Heather Mubarak
      April 27, 2020 at 8:27 pm

      Hi Lauren – I haven’t made this in a regular cake pan or pie pan but you could certainly try that. Let me know how it goes!

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