Chocolate Mousse Cake

Updated: Feb 16, 2026 by christina.marsigliese · 85 Comments

You have found the chocolate cake that ends all chocolate cakes! This incredible dessert is chocolate HEAVEN, designed for chocolate purists, chocoholics, chocolate addicts... whatever you want to call us! My Chocolate Mousse Cake is outrageously decadent and delicious with rich, moist chocolate cake topped with a thick layer of dark chocolate mousse. As decadent as it is, it is also so light and airy. The best part is how easy this recipe is with a simple one bowl cake batter and no fuss chocolate mousse that doesn't contain any raw egg. You will impress anyone you serve this too, and you'll feel like a star since it's not that hard. If you love chocolate cake, make sure you check out my Best Moist Chocolate Cake, One Bowl Chocolate Sheet Cake and Ultimate Moist Chocolate Fudge Cake.

side view of side view of chocolate mousse cake slice

WHY THIS RECIPE WORKS

Easy to make - the chocolate cake batter is so simple. You just mix all of the ingredients in one bowl and bake.
Super moist chocolate cake - the cake is super moist! It has a soft texture and fine crumb that stays moist for days without drying out, and it is even moist when cold from the fridge as necessary since this cake should be stored chilled.
Rises flat - this cake rises nice and even so you have a flat surface to layer on the mousse which makes for easy preparation and clean presentation.
Light and airy chocolate mousse - you will find the texture of this chocolate mousse to be irresistible as it melts in your mouth.
Rich chocolate flavor - both the cake and mousse have a smooth and rich chocolate taste.

angle view of sliced chocolate mousse cake

INGREDIENTS FOR CHOCOLATE MOUSSE CAKE

Here are some notes about the ingredients. For a full list of ingredients, check out the recipe card at the bottom of the page.

All purpose flour - you do not need specialty cake flour to make a wonderful chocolate cake. Just be sure to measure your flour correctly. Adding too much flour is the most common mistake and leads to tough and dry cake. The most accurate way to measure flour is using a scale. If you don't have one then fluff your flour with a spoon, spoon it into your measuring cup and use a knife to level it off. This batter is meant to be thin so refrain from adding more flour to make it thicker.
Granulated sugar - simple white sugar will keep this cake moist and tender.
Pure vanilla extract - vanilla is important to enhance the flavor of chocolate.
Cocoa powder - I recommend getting some good quality cocoa powder. It's the main flavor and you want it to shine so use the best you can find. I love to use this Dutch Process cocoa powder for this recipe. Make sure you use unsweetened cocoa powder and not cocoa mix.
Eggs - one whole egg will set the structure of this cake and help emulsify the batter. You'll also need 3 egg yolks for the mousse.

top view of chocolate mousse cake dusted with cocoa powder before slicing

top view of chocolate mousse cake dusted with cocoa powder after slicing

Oil - this is an oil-based cake because oil is liquid at room temperature (it's an unsaturated fat) which means that the cake will still be soft when it's cold.
Sour cream - one of the secrets to this moist chocolate cake is sour cream! It contributes the dairy undertones, rich flavor and body (thanks to its high protein and fat content) that oil-based cakes lack. Full fat sour cream adds richness and dairy notes to this cake in the absence of butter.
Milk - you'll need milk for the cake batter and also for the chocolate mousse layer. It forms the base of the custard for the mousse and I recommend whole milk.
Dark chocolate - you'll need pure dark chocolate to make the chocolate mousse. Anything between 50 and 70% cocoa solids will work, but I highly recommend dark chocolate with 60% cocoa solids. You can blend semisweet chocolate with my favorite bittersweet chocolate callets which are very convenient.
Milk chocolate - a bit of milk chocolate contributes additional milk solids for more body.
Whipping cream - look for whipping cream or "heavy" cream with 35% milkfat to make the chocolate mousse truffle layer and the chocolate ganache glaze.

STEP BY STEP INSTRUCTIONS: HOW TO MAKE CHOCOLATE MOUSSE CAKE

STEP 1). Make the cake base. Combine dry ingredients. Sift flour, cocoa powder, baking powder and baking soda into a medium bowl. Add sugar and salt, then whisk to blend evenly.
STEP 2). Add wet ingredients. Make a well in the center of the dry ingredients, then add oil, beaten egg, sour cream, milk and vanilla extract and slowly whisk it in until combined and the batter is smooth.
STEP 3). Bake. Spread batter evenly into prepared pan using a small offset spatula and bake for 20-25 minutes until a skewer inserted into the center comes out clean. Transfer to a wire rack and let cool completely in the pan. Trim the top of the cake to level it out and make it flat if necessary, but I never need to because it always bakes up nice and flat.
STEP 4). Make the mousse. Place finely chopped dark chocolate and milk chocolate in a medium heatproof bowl and set aside. Place the milk in a heatproof measuring jug and microwave until steaming. You can also heat it in a saucepan but be sure to cover the pot so you don't loose too much water through evaporation.
STEP 5). Make custard. Combine egg yolks and sugar in a 1 quart stainless steel saucepan (this is my go-to pouring saucepan that everyone asks me about) and whisk until smooth and evenly blended. Very slowly pour in the milk while whisking until it is all combined. Transfer the pot to the stove and stir constantly using a rubber spatula or wooden spoon over medium-low heat for 5-7 minutes until it thickens. It should coat the back of a spoon like thick cream. Immediately pour the hot custard over the chocolate, add salt and stir until smooth and the chocolate is completely melted. If necessary, (like if it is cold in your house) place the bowl in the microwave and heat on low power for just 20-30 seconds to melt any residual pieces of chocolate. Let cool for about 10-15 minutes so it is no longer hot.
STEP 6). Fold in cream. Place cold cream in a medium bowl and use an electric hand mixer to whip to medium peaks which is somewhere between soft and stiff peaks. When you lift the beaters, the cream chocolate curl just slightly when it reaches this stage. Take one third of the whipped cream and fold it evenly into the chocolate custard to lighten it up. You don't need to be too gentle at this first stage. Gently fold in the remaining cream in 2 stages being careful not to deflate the air. Watch the video tutorial to see the folding technique I use.
STEP 7). Assemble the cake. Spoon the mousse over the cooled cake still in the pan and spread it out evenly using a small offset spatula. Place it in the fridge for at least 4 hours to set.

WHAT IS THE DIFFERENCE BETWEEN DUTCH COCOA POWDER AND NATURAL COCOA POWDER?

Dutch cocoa powder is cocoa powder that has been treated with an alkalizing agent (a basic ingredient) such as potassium carbonate or sodium carbonate. This treatment, combined with certain parameters of pressure and temperature will increase the pH (decrease the acidity) of the cocoa powder to give it a less sour taste, darken the color and help it become more dispersible in water. My preferences for Dutch cocoa powder ones with a higher fat content and they are this Cacao Barry Extra Brute, Ghirardelli Majestic and Green & Blacks Organic.
Natural cocoa has not been alkalized and is 100% cocoa powder. It has a lighter color and has a very lovely fruity flavor with some pleasant acidity and slight bitterness that is inherent to the cocoa bean. My preferences for natural cocoa are Ghirardelli 100% Cocoa and Hershey's Unsweetened.

side view of chocolate mousse cake showing cross section

WHAT IS CHOCOLATE MOUSSE?

Chocolate mousse is a classic French dessert that doesn't require any baking. It is a rich dish traditionally prepared with raw eggs by first blending melted chocolate with butter or water and stirring in egg yolks. The dense chocolate mixture is lightened up by folding in whipped egg whites and/or whipped cream. My recipe for chocolate mousse does not have raw eggs so it is acceptable for anyone to consume. I prepare it by first making a custard with egg yolks, sugar and milk, then mixing in chocolate while it is hot so it melts. I fold in cold whipped cream instead of raw egg whites and the result is fluffy, airy and so creamy.

side view of side view of sliced chocolate mousse cake

EXPERT BAKING TIPS

Use a neutral tasting oil like pure sunflower oil for the cleanest flavor to let the chocolate taste stand out.
Do not reduce the sugar. The right amount of sugar will make cake moist because it binds water so that it stays tightly in the batter and doesn't evaporate excessively during baking. The right amount of sugar keeps the cake tender even when served cold.
Keep an eye on the baking time. Set a timer for the first time stated in the recipe and check with a skewer - it should come out clean.
Stir the ganache gently. Do not whip the cream and chocolate when making the ganache for the truffle layer or it will cause the milkfat and the cocoa butter to separate.
Whip the cream just to soft peaks. This will create a delicate soft truffle filling. If you over-whip the cream, it may give the mousse a grainy texture.

side view of sliced chocolate mousse cake showing cross section

RECIPE FAQ

What type of oil is best for chocolate cake?

Firstly - use a fresh oil! Do not use anything that's been opened for a long time and when you store oil, it should be in a cool dark place. Light and heat accelerate oxidation reactions that can make the flavor turn rancid. My oil of choice for baking is sunflower oil for its clean and neutral taste, but any other oil such as canola or safflower will do. You can even use olive oil, but keep in mind that it will add the taste of olive oil to the cake.

Which cocoa powder is best for chocolate mousse cake?

This recipe works with both Dutch process and natural cocoa powder. For a darker color like in this photo, I use high fat Dutch cocoa powder. My absolute preference is this one and this one. The first one is rich with a deep color while still having some nice complex fruity notes which some Dutch cocoa powders can lack. Natural cocoa has a wonderful fruity flavor and I like to use it as well. You can use Hershey's natural cocoa or this one that I love.

What is a substitute for sour cream?

Sour cream really makes this cake delicious, but if sour cream is not available to you where you live, you can also make this recipe using an equal amount of full fat Greek yogurt. I have tested this and it worked well! Another suitable substitution is crème fraîche which is a type of fermented dairy product somewhere between yogurt and sour cream.

What is the secret to super moist cake and how do I make my cake more moist?

It's not more fat! Moisture comes from liquid, not fat. So you can add more butter and more oil, but it will really just make the cake more dense and more tender by shortening the texture. Fat will not make a cake moist as only liquids can add moisture. This cake is moist because of the amount of liquid.

How do you add moisture to a chocolate cake?

I normally scoff at a cake recipe that uses only oil and no butter since butter is superior for its flavor. However, oil makes the texture very soft and in turn gives the perception of "moistness". That's because oil is made up of mostly unsaturated fats that are liquid at room temperature. Butter contains more saturated fats that are solid at room temperature, therefore the texture of a butter cake will be more crumbly and firm.

Can I make this chocolate cake recipe with a round pan?

Yes, you can make this cake in a 9-inch round pan. If you use an 8-inch round pan the cake and mousse layers will be taller and the cake will take longer to bake. If you use a 9x9-inch square pan, the cake layer and the truffle layer will be thinner.

Can I double the chocolate mousse recipe?

If you want an extra thick and tall chocolate mousse layer, you can double all of the quantities. The only difference is that it will take slightly longer to chill and you may want to use an acetate strip to hold it in.

Can I freeze chocolate mousse cake?

I would not recommend freezing this whole cake as the mousse topping will have a very different texture once thawed. However, you can freeze the cooled cake base. Just wrap it well in plastic and then store in a freezer bag in the freezer for up to 3 months.

If you love cake, check out these recipes!

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