Chocolate Mousse Cake

5 from 21 votes

This easy Chocolate Mousse Cake is so moist, decadent, and impressive! Nobody would ever guess how simple the cake and mousse filling are to make!

Prep Time30

Cook Time25

Additional time30

Total Time1 25

Course: Dessert

Cuisine: American

Servings:

1 15.25 oz Box Devils Food Cake Mix (We used Duncan Hines Devils Food Cake- Perfectly Moist
½ cup (60g) All Purpose Flour
½ cup (100g) sugar
1 3.9 oz small box Chocolate Instant Pudding Mix. (We use Jello Brand-Do not make pudding, just add the dry powder.)
1 cup (227g) Sour Cream
½ cup (108g) Vegetable Oil (we use canola)
1 ¼ cup (302g) water
3 large eggs room temperature
2 ½ teaspoons (10g) vanilla extract

1 small box instant chocolate pudding 3.9 oz- We recommend sifting the Pudding Mix (to prevent graininess)
2 cups heavy cream or whipping cream

3 sticks (339g total) Unsalted Butter, softened (Do not soften in the microwave. You can slice butter into small slices and lay flat on wax paper to speed up softening.)
7 cups powdered sugar adjust slightly up or down to your liking
1 cup (82g) unsweetened cocoa
¾ cup (180g) milk plus additional as needed for desired consistency (add in very small increments)
2 teaspoons (12g) vanilla extract
1 teaspoon (6g) salt

Preheat the oven to 325 degrees F. Grease and Flour three 8 inch round pans. As an optional step, we also like to line the bottom of our pans with parchment paper.
In the bowl of your mixer, add the chocolate cake mix, all purpose flour, sugar, and chocolate pudding mix. Whisk to blend.
Add the remaining ingredients to the bowl (sour cream, vegetable oil, water, eggs, and vanilla). Mix on low speed for about 30 seconds.
Scrape down the sides and bottom of the bowl as needed and mix on medium speed for two minutes. The batter should look well blended.
Bake at 325℉ for approximately 20-25 minutes or until the layers spring back when lightly touched, or a toothpick can be inserted and removed with just a few moist crumbs attached. Baking times may vary depending on your oven and the type of pans used. Dark pans may bake slightly more quickly.
Allow the baked cake layers to cool in their pans on a wire rack for 10 minutes before turning out. Make sure that they are completely cool before frosting!

Combine the sifted chocolate pudding mix and heavy cream in a mixing bowl. I prefer to mix with a hand held mixer, but a whisk is fine too. If using a mixer, start on low speed until well combined.
Then, switch to high speed and whip the pudding until thick and fluffy. If mousse is too thick, add more heavy cream bit by bit until you reach a nice, easily spreadable consistency.
If mixing by hand, simply whisk rapidly for a couple of minutes or until mixture is nice and thick (but still very easily spreadable). Refrigerate until ready to use.

Add butter and mix on low to medium speed until smooth. Add vanilla and blend into the butter. Add powdered sugar, salt, and sifted cocoa powder.
Add most of the milk. Begin mixing at low speed so you won't have a cloud of powdered sugar in your kitchen.
Continue to mix adding remaining milk as needed. It may take 5 to 6 minutes to reach the smoothness and consistency you like. It will take longer if using a hand mixer. As you mix the frosting will become very smooth. You can add additional milk (1 Tablespoon at a time) if the frosting is too thick or additional powdered sugar if too soft.

Place the first chocolate cake layer on the cake base or pedestal. Spread with chocolate mousse filling. Our filling was still fairly thick-- if you added more cream to create a softer consistency of mousse, it is a good idea to pipe a dam of buttercream around the edge of the cake layer about ¼-1/2 inch from the edge, using a piping bag with the tip snipped away. Then, spread the mousse onto the cake within the dam.
Top with the second cake layer and repeat. Top with the third cake layer and fill in any remaining gaps between the cake layers with chocolate buttercream.
Crumb coat the top and sides of the cake with a thin layer of buttercream. At this point, we like to chill the cake in the freezer for 15 minutes or in the refrigerator for longer, to firm everything up. Then, add the final layer of buttercream and decorate to your liking.
We added texture with a small offset spatula, and then piped a top border of rosettes and starts using a 1M piping tip.

This cake should be refrigerated because of the cream filling. It is best to use an airtight container or cake dome.

However, for best flavor and texture, it is best to remove the cake from the refrigerator a couple of hours before serving.