We have a decadent new recipe to share: an easy Chocolate Mousse Cake that will delight chocolate lovers. Surprisingly simple to make, this show-stopping cake starts with a boxed cake mix and a few pantry staples.
Rich chocolate cake layers are filled with a luscious, quick chocolate mousse and finished with a silky chocolate buttercream. The combination is ultra moist, intensely chocolatey, and impressive for any occasion.
Table of Contents
Why we Love it
There are many reasons this cake is a favorite:
- Simple to prepare from a boxed mix yet elegant and impressive.
- A triple dose of chocolate: cake, mousse filling, and buttercream.
- Ultra moist texture thanks to a few add-ins that boost flavor and crumb.
- Perfect for birthdays, holidays, or any celebration.
Ingredients for Chocolate Mousse Cake Layers
The chocolate layers use a boxed Devil’s Food cake mix doctored with a few additions so you get a rich, moist cake and enough batter to fill three 8-inch pans.
Tips for Ingredients
Key tips to get the best results:
Instant chocolate pudding: Adding the dry pudding mix deepens chocolate flavor and creates a tender crumb. Use the dry powder—do not prepare it as pudding.
Devil’s food cake mix: We used a Perfectly Moist variety, but any quality chocolate cake mix will work.
Sour cream: Full-fat sour cream adds richness and improves texture. It’s a common ingredient in doctored cake mixes for a moister cake.
How to Make Chocolate Mousse Cake
Here’s a quick overview of the process—see the full recipe at the end of this page.
- Preheat the oven to 325°F. Grease and flour three 8-inch round pans; lining the bottoms with parchment is optional but helpful.
- In a mixer bowl, whisk together the chocolate cake mix, all-purpose flour, sugar, and instant chocolate pudding powder.
- Add sour cream, vegetable oil, water, eggs, and vanilla. Mix on low for about 30 seconds, scrape the bowl, then mix on medium for two minutes until smooth.
- Divide the batter among the prepared pans and bake 20–25 minutes, or until a toothpick comes out with a few moist crumbs and layers spring back when touched.
- Cool the layers in the pans for 10 minutes, then turn out onto a wire rack and cool completely before assembling.
Easy Chocolate Mousse Filling
The filling is a fast “mock mousse” made from instant chocolate pudding mix and heavy cream. Whip the sifted pudding mix with chilled heavy cream until thick and fluffy. If it’s too thick, add a little more cream until it becomes easily spreadable. The result is light, creamy, and perfect between cake layers.
Chocolate Frosting
Finish the cake with a classic chocolate buttercream: softened unsalted butter beaten with sifted cocoa powder, powdered sugar, a splash of milk, vanilla, and a pinch of salt. Beat until smooth and spreadable. Adjust milk or powdered sugar a tablespoon at a time to reach the desired consistency.
Assembling the Chocolate Mousse Cake
Make sure the cake layers are completely cool (room temperature or chilled) before assembling. Place the first layer on your cake base and spread a layer of mousse. If your mousse is on the soft side, pipe a small buttercream dam around the edge to contain it. Otherwise, simply spread the mousse evenly.
Repeat with the second layer, finish with the third, then fill any gaps with buttercream. Apply a thin crumb coat of buttercream to top and sides, chill the cake briefly to set the crumb coat (about 15 minutes in the freezer or longer in the refrigerator), then add the final layer of buttercream.
Decorating the Cake
After chilling, apply the final buttercream layer and add texture with an offset spatula. For a polished finish, pipe a border of stars and rosettes along the top edge with a 1M tip.
Recipe FAQs
Yes. Wrapped tightly in plastic wrap and foil, baked layers will keep in the freezer for up to three months. We recommend placing each layer on a foil-wrapped cake board, then wrapping in plastic and foil. To thaw, move the wrapped layers to the counter for 30–45 minutes, then unwrap and finish thawing as needed. Some bakers assemble with layers slightly frozen for easier handling.
Yes. Because of the cream-based mousse filling, store the cake refrigerated in an airtight container or cake dome. For best flavor and texture, remove the cake from the fridge a couple of hours before serving to allow it to come closer to room temperature.
Yes. While a Devil’s Food mix was used here, you can use your preferred brand of chocolate cake mix. Baking times may vary slightly by mix and pan type.
While this recipe uses a doctored mix, there are several from-scratch chocolate cake and mousse recipes that offer similar decadent results. You can also use the mousse filling with any scratch chocolate layer cake if you prefer to bake from scratch.
Yes. You can make this as a two-layer 9-inch cake or adapt it to a 9×13 sheet pan. As a rule, do not fill pans more than two-thirds full. Adjust baking time accordingly based on pan size and depth.
More Chocolate Cakes
If you love chocolate, try other favorites like Black Forest Cake, German Chocolate Cake, or a classic Triple Chocolate Cake. These variations showcase different fillings and textures while keeping chocolate front and center.
-
Black Forest Cake Recipe
-
Chocolate Buttermilk Cake
-
German Chocolate Cake Recipe
-
Marble Cake (from Cake Mix)
Thanks for stopping by! We hope you enjoy this easy Chocolate Mousse Cake—it’s a decadent, crowd-pleasing dessert that’s simpler than it looks and perfect for chocolate lovers.
Chocolate Mousse Cake
Ingredients
- 1 (15.25 oz) box Devil’s Food cake mix
- ½ cup (60g) all-purpose flour
- ½ cup (100g) sugar
- 1 (3.9 oz) small box instant chocolate pudding mix (dry)
- 1 cup (227g) sour cream
- ½ cup (108g) vegetable oil
- 1 ¼ cup (302g) water
- 3 large eggs, room temperature
- 2 ½ teaspoons (10g) vanilla extract
For the Easy Chocolate Mousse Filling
- 1 small box instant chocolate pudding (3.9 oz), sifted
- 2 cups heavy cream or whipping cream
For the Chocolate Buttercream
- 3 sticks (339g total) unsalted butter, softened
- 7 cups powdered sugar (adjust to taste)
- 1 cup (82g) unsweetened cocoa powder, sifted
- ¾ cup (180g) milk, plus more as needed
- 2 teaspoons (12g) vanilla extract
- 1 teaspoon (6g) salt
Instructions
Instructions
- Preheat oven to 325°F. Grease and flour three 8-inch round pans and line bottoms with parchment if desired.
- Whisk together the cake mix, flour, sugar, and dry pudding mix in a mixer bowl.
- Add sour cream, oil, water, eggs, and vanilla. Mix on low for 30 seconds, scrape the bowl, then mix on medium for 2 minutes.
- Divide batter among pans and bake 20–25 minutes or until a toothpick comes out with a few moist crumbs and layers spring back to the touch.
- Cool in pans for 10 minutes, then turn out onto a wire rack and cool completely before frosting.
Chocolate Mousse Filling
- Combine sifted pudding mix and heavy cream in a bowl. Start on low if using a mixer, then increase to high and whip until thick and fluffy. If too thick, add cream a little at a time to reach a spreadable consistency. Refrigerate until ready to use.
Chocolate Buttercream
- Beat butter until smooth. Add vanilla. Gradually add powdered sugar, salt, and sifted cocoa. Add most of the milk and mix starting on low, then increase speed. Continue mixing 5–6 minutes until smooth, adding milk or powdered sugar to adjust consistency.
Assembling and Decorating the Cake
- Place the first cake layer on a cake board or stand and spread mousse. If mousse is soft, pipe a ¼–½-inch buttercream dam before adding mousse.
- Top with the second layer and repeat. Add the third layer, fill gaps with buttercream, and apply a thin crumb coat. Chill 15 minutes in the freezer or longer in the refrigerator to set.
- Finish with a final layer of buttercream, add texture with an offset spatula, and pipe a top border of rosettes or stars using a 1M tip.
Notes
This cake must be refrigerated because of the cream filling. Store in an airtight container or cake dome. For best flavor and texture, remove the cake from the refrigerator a couple hours before serving so it can warm closer to room temperature.