This incredible chocolate mousse cake is made with moist chocolate cake, light and creamy eggless chocolate mousse, and a silky chocolate ganache.
This viral chocolate mousse cake has over 5 million views on Instagram and is a favorite treat for hundreds of bakers!
As a pastry chef, I made sure this is the best recipe you will ever try. The cake base stays soft and moist for days because we use oil instead of butter and mix the cocoa with hot coffee.
Combined with a fluffy, eggless chocolate mousse and a shiny chocolate topping, this cake is a family favorite.
For more delicious chocolate cake recipes, check out my chocolate Oreo cake, chocolate brooklyn blackout cake, chocolate caramel cake, Matildas chocolate cake
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Why this recipe works
- One-Bowl Cake Base: The chocolate cake batter is incredibly simple. You just whisk all the ingredients together in a single bowl and bake—no fancy mixer required.
- Stays Moist When Cold: Because I use liquid oil and sour cream instead of butter, the cake base stays soft, tender, and ultra-moist even when stored cold in the fridge.
- Glossy 2-Ingredient Ganache: The top layer is a foolproof blend of dark chocolate and heavy cream. It creates a smooth ganache that adds a rich, velvety finish to every single bite.
- No-Cook Fluffy Mousse: The eggless chocolate mousse skips the finicky stovetop custard step. It is stabilized effortlessly with gelatin so it holds a perfect shape when sliced.
- Deep Gourmet Flavor: Blooming Dutch-process cocoa powder in hot coffee unlocks a rich, dark, and smooth chocolate taste that rivals any professional pastry shop.
Ingredients
Before you start to make this recipe, measure and prepare your ingredients so the cooking process will go smoothly and easily.
Full measurements are in the recipe card below.
The One-Bowl Chocolate Cake
- All-Purpose Flour: Provides the perfect structure for the cake base. Always measure with a kitchen scale to prevent a dense or dry crumb.
- Granulated Sugar: Sweetens the cake and locks in essential moisture to keep the texture tender.
- Dutch-Process Cocoa Powder: Gives the cake its intensely dark color and a smooth, mellow chocolate flavor.
- Baking Powder & Baking Soda: The leavening agents that help the cake rise evenly.
- Vegetable Oil: The secret to a cake that stays incredibly soft and moist even when stored cold in the fridge.
- Egg: One large egg binds the ingredients together and builds the cake's structure.
- Sour Cream & Buttermilk: Their natural acidity breaks down gluten for an ultra-tender crumb, adding rich dairy notes without butter.
- Hot Coffee: Hydrates or "blooms" the cocoa powder to unlock trapped flavor compounds. Note: Your cake will not taste like coffee!
The Eggless Chocolate Mousse Layer
- Dark Chocolate (60% Cocoa): Use high-quality chocolate bars (not chocolate chips) for a smooth, professional melt.
- Heavy Whipping Cream (35% Fat): Whisked to medium peaks, creating a light, airy, and fluffy texture.
- Unflavored Gelatin Powder: Bloomed in a splash of water to naturally stabilize the egg-free mousse so it holds its shape perfectly for slicing.
The Glossy Chocolate Ganache Glaze
- Heavy Cream: Heated and poured over the chocolate to create a smooth, shiny, and decadent mirror-like topping.
- Dark or Semi-Sweet Chocolate: Finely chopped to ensure it melts evenly into the cream.
Instructions
Bake the One-Bowl Chocolate Cake Base
Preheat your oven to 180°C (350°F). Line a 9-inch springform pan with parchment paper and grease with cooking spray.
In a large mixing bowl, combine the eggs, buttermilk, oil, vanilla extract, kosher salt, granulated sugar, and sour cream. Sift in the first half of the cocoa powder and whisk until completely smooth.
Sift the flour into the bowl, add the baking powder and baking soda, and whisk until almost combined.
In a separate cup, stir the remaining half of the cocoa powder into the hot coffee to bloom it. Pour this hot coffee mixture into your main batter bowl and gently stir until smooth, fluid, and free of lumps.
Pour the chocolate batter into your prepared pan. Bake for 22–25 minutes. The cake is done when a toothpick inserted into the center comes out clean with just a few moist crumbs.
Transfer the pan to a wire rack and let the cake cool completely to room temperature.
Create the Stabilized Chocolate Mousse
In a small bowl, mix the water and unflavored gelatin powder. Let it sit for 10 minutes to bloom and thicken.
Combine the dark chocolate and heavy cream in a medium mixing bowl. Microwave in short 10-to-20-second bursts, stirring between each, until completely melted. (Alternatively, melt over a double boiler/bain-marie).
Whisk the melted chocolate and cream vigorously or use an immersion blender until the mixture is shiny, smooth, and perfectly emulsified.
In a separate large mixing bowl, combine the cold heavy cream, sifted cocoa powder, powdered sugar, and vanilla extract. Whip until it reaches soft peaks with a thick, yogurt-like consistency.
Microwave the bloomed gelatin for 5 seconds until fluid (do not overheat!). Whisk the melted gelatin into your warm chocolate mixture.
Stir ½ cup of your whipped cream into the chocolate base to lighten it.
Gently fold the remaining chocolate mixture into the whipped cream in two separate batches using a rubber spatula. Fold just until homogeneous and streak-free to retain maximum air.
Release the cooled cake from the springform ring. Use a serrated knife or cake leveler to trim off any unevenness on the top so it is perfectly flat.
Place the leveled cake back into the clean springform pan. Slide a sheet of acetate cake collar down the sides of the pan, wedging it gently between the cake and the pan wall. Ensure the collar extends about an inch above the pan rim.
Pour the fluffy chocolate mousse directly over the cake layer. Smooth the surface with an offset spatula and refrigerate for at least 5 hours, or ideally overnight, to set.
Combine dark chocolate and heavy cream in a small bowl and microwave for 70 seconds. Let it sit undisturbed for 10 minutes, then stir gently until a glossy, silky ganache forms.
Release the springform ring and gently peel away the acetate collar.
Pour the slightly warm ganache directly onto the center of the chilled cake. Use your offset spatula to nudge it elegantly over the edges.
Return the cake to the fridge for 30 minutes to let the ganache set. Slice with a warm knife and enjoy!
Expert Tips
- Use Neutral Oils Only: Select flavorless oils like canola, safflower, or sunflower oil. Avoid olive or coconut oils, which leave strong aftertastes that mask the rich chocolate flavor.
- Do Not Reduce the Sugar: Sugar functions as a liquid tenderizer and hydrator. Reducing the amount will alter the chemical structure, resulting in a dry, crumbly cake base once chilled.
- Test for Moist Crumbs: Start checking the cake 2 minutes before the baking time ends. A toothpick inserted into the center should come out with a few damp, clinging crumbs—not completely clean, which indicates overbaking.
- Stir the Ganache Slowly: Mix the melted cream and chocolate gently with a rubber spatula. Vigorous whisking incorporates air pockets and forces the cocoa butter to separate, creating a dull, greasy glaze.
- Whip Cream to Medium Peaks: Stop whipping the heavy cream when it reaches a thick, yogurt-like consistency. Over-whipped, stiff cream loses its elasticity and turns grainy when folded into the chocolate base.
Troubleshooting
Why did my chocolate cake sink in the center?
- The Cause: Opening the oven door too early causes a sudden drop in temperature before the cake's structure sets. Alternatively, your baking powder or baking soda may be expired.
- The Fix: Keep the oven door closed for at least the first 20 minutes of baking. Test your leaveners for freshness by dropping a pinch of baking powder into hot water; it should fizz immediately.
Why is my chocolate mousse grainy or lumpy?
- The Cause: Either the heavy cream was over-whipped, or the melted chocolate mixture was too cold when folded into the cream, causing the chocolate to freeze and seize into tiny solid bits.
- The Fix: Ensure your melted chocolate base is completely smooth and slightly warm to the touch before combining. If it cooled too much while sitting, microwave it for 5–10 seconds.
Why is my mousse too soft and not holding its shape?
- The Cause: The unflavored gelatin didn't bloom properly, or it was overheated in the microwave. Boiling gelatin destroys the proteins that allow it to set.
- The Fix: Let the gelatin sit in cold water for a full 10 minutes to bloom. When melting it, use short 5-second bursts just until it liquefies—never let it boil.
Why is my chocolate ganache split, oily, or dull?
- The Cause: The heavy cream was too hot when poured over the chocolate, breaking the emulsion, or the mixture was stirred too fast.
- The Fix: Warm 1 tablespoon of milk or cream in a separate bowl. Slowly whisk the split, oily ganache into the warm milk one tablespoon at a time until the glossy, smooth emulsion restores.
Faq's
Chocolate mousse is a soft, fluffy dessert made by mixing melted chocolate with whipped cream. It is full of tiny air bubbles, which makes it melt in your mouth.
It must always be served cold straight from the fridge. The cream and chocolate need to stay cold to keep their shape. If left out on the counter, the mousse will melt and turn runny.
The plastic collar acts like a wall. It holds the liquid mousse in place on top of the cake until it sets firm in the fridge. When you peel it off, you get perfectly smooth, clean sides.
Dip a sharp knife into hot water, wipe it dry with a towel, and make one quick slice. Clean and reheat the knife in the hot water before making your next cut so the layers do not smear.
Storing
Keep this cake in the fridge for up to 4 to 5 days in a sealed container so it does not smell like other fridge food. Do not leave it out on the counter for more than 1 or 2 hours, or the mousse layer will melt.
Freezing
You can freeze this cake for up to 2 months after it has set firm. You can freeze the whole cake or cut it into slices first.
If you freeze slices, wrap them in plastic wrap, put them in a ziplock bag, and place them inside a plastic container so they do not get freezer burn.
Make it ahead of time
You can make this cake 1 or 2 days before you need it and keep it in the fridge in a covered container.
You can also make the whole cake and freeze it 1 month early, then just let it thaw in the fridge overnight before you want to eat it.
Substitutions
Gluten-Free: Replace the all-purpose flour with a 1:1 gluten-free baking flour blend that contains xanthan gum.
Dairy-Free: Use plant-based butter or oil for greasing, and swap the buttermilk, sour cream, heavy cream, and milk for unsweetened dairy-free alternatives (like coconut cream or almond milk). Ensure your dark chocolate is dairy-free.
Buttermilk Substitute: Mix 1 cup of milk with 1 tablespoon of lemon juice or white vinegar. Let it sit for 5 minutes until it gets thick and sour, then use it.
Coffee: You will not taste the coffee; it just makes the chocolate taste stronger. You can use decaf coffee or plain hot water instead to make it kid-friendly.
Variations
White Chocolate Mousse: Swap the dark chocolate in the mousse layer for high-quality white chocolate baking bars to create a beautiful color contrast.
Mocha Mousse: Mix 1 teaspoon of espresso powder into the heavy cream before whipping it to give the mousse a rich coffee flavor.
Berry Mousse: Press fresh raspberries or sliced strawberries directly into the top of the cooled cake layer before pouring the chocolate mousse over it.
Equipment
- 9-Inch Springform Pan: Needed to release the delicate mousse cake without flipping it upside down.
- Acetate Cake Collar: A clear plastic strip that lines the pan so the fluid mousse sets with smooth, straight sides.
- Serrated Knife or Cake Leveler: Used to trim the bumpy top off the cake layer so it sits perfectly flat.
- Offset Spatula: A flat metal tool used to spread the mousse and push the ganache glaze over the edges.
- Fine-Mesh Sieve: Used to remove lumps from the cocoa powder and flour for a smooth batter.
- Digital Kitchen Scale: Used to weigh flour and chocolate accurately to ensure the cake stays moist.
More mousse recipes
Mango Mousse- This easy mango mousse has a smooth, creamy texture and a sweet, tangy, fresh mango flavor.
Peanut Butter Mousse- A rich and creamy peanut butter mousse recipe with an irresistible, velvety texture.
Chocolate Parfait- Features layers of homemade chocolate mousse, whipped cream, and crunchy chocolate cookie crumbs.
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📖 Recipe
Most Amazing Chocolate Mousse Cake
Ingredients
For the chocolate cake
- ¾ cup Granulated sugar
- 1 teaspoon Vanilla extract
- ¼ teaspoon Kosher salt
- ⅓ cup Vegetable oil
- 1 Egg
- 1 Egg yolk
- ⅓ cup Sour cream
- ⅓ cup Buttermilk
- ⅓ cup Cocoa powder Dutch processed
- 1 cup Flour AP, plain flour
- ¼ teaspoon Baking soda
- 1 teaspoon Baking powder
- ½ cup Coffee hot
For the chocolate mousse
Melt together:
- 7.05 oz Dark chocolate 60%
- 4.2 oz heavy cream
Whip together
- 1 ¾ cups Heavy cream cold
- 1 teaspoon Vanilla extract
- 2 tablespoon Cocoa powder Dutch processed
- 3 tablespoon Powdered sugar
Gelatin:
- 7 g Gelatin powder
- 42 g Water
For the chocolate ganache
- 5.2 oz Heavy cream
- 5.2 oz Dark chocolate
Instructions
Bake the One-Bowl Chocolate Cake Base
- Preheat your oven to 180°C (350°F). Line a 9-inch springform pan with parchment paper and grease with cooking spray.
- In a large mixing bowl, combine the eggs, buttermilk, oil, vanilla extract, kosher salt, granulated sugar, and sour cream. Sift in ½ of the cocoa powder and whisk until completely smooth.
- Sift the flour into the bowl, add the baking powder and baking soda, and whisk until almost combined.
- In a separate cup, stir the remaining half of the cocoa powder into the hot coffee to bloom it. Pour this hot coffee mixture into your main batter bowl and gently stir until smooth, fluid, and free of lumps.
- Pour the chocolate batter into your prepared pan. Bake for 22–25 minutes. The cake is done when a toothpick inserted into the center comes out clean with just a few moist crumbs.
- Transfer the pan to a wire rack and let the cake cool completely to room temperature.
Create the Stabilized Chocolate Mousse
- In a small bowl, mix the water and unflavored gelatin powder. Let it sit for 10 minutes to bloom and thicken.
- In a large mixing bowl, combine the eggs, buttermilk, oil, vanilla extract, kosher salt, granulated sugar, and sour cream. Sift in the first half of the cocoa powder and whisk until completely smooth.
- In a separate large mixing bowl, combine the cold heavy cream, sifted cocoa powder, powdered sugar, and vanilla extract. Whip until it reaches soft peaks with a thick, yogurt-like consistency.
- Microwave the bloomed gelatin for 5 seconds until fluid (do not overheat!). Whisk the melted gelatin into your warm chocolate mixture.
- Stir ½ cup of your whipped cream into the chocolate base to lighten it.
- Gently fold the remaining chocolate mixture into the whipped cream in two separate batches using a rubber spatula. Fold just until homogeneous and streak-free to retain maximum air.
- Release the cooled cake from the springform ring. Use a serrated knife or cake leveler to trim off any unevenness on the top so it is perfectly flat.
- Place the leveled cake back into the clean springform pan. Slide a sheet of acetate cake collar down the sides of the pan, wedging it gently between the cake and the pan wall. Ensure the collar extends about an inch above the pan rim.
- Pour the fluffy chocolate mousse directly over the cake layer. Smooth the surface with an offset spatula and refrigerate for at least 5 hours, or ideally overnight, to set.
- Combine dark chocolate and heavy cream in a small bowl and microwave for 70 seconds. Let it sit undisturbed for 10 minutes, then stir gently until a glossy, silky ganache forms.
- Release the springform ring and gently peel away the acetate collar.
- Pour the slightly warm ganache directly onto the center of the chilled cake. Use your offset spatula to nudge it elegantly over the edges.
- Return the cake to the fridge for 30 minutes to let the ganache set. Slice with a warm knife and enjoy!
Notes
- Use Neutral Oils Only: Select flavorless oils like canola, safflower, or sunflower oil. Avoid olive or coconut oils, which leave strong aftertastes that mask the rich chocolate flavor.
- Do Not Reduce the Sugar: Sugar functions as a liquid tenderizer and hydrator. Reducing the amount will alter the chemical structure, resulting in a dry, crumbly cake base once chilled.
- Test for Moist Crumbs: Start checking the cake 2 minutes before the baking time ends. A toothpick inserted into the center should come out with a few damp, clinging crumbs—not completely clean, which indicates overbaking.
- Stir the Ganache Slowly: Mix the melted cream and chocolate gently with a rubber spatula. Vigorous whisking incorporates air pockets and forces the cocoa butter to separate, creating a dull, greasy glaze.
- Whip Cream to Medium Peaks: Stop whipping the heavy cream when it reaches a thick, yogurt-like consistency. Over-whipped, stiff cream loses its elasticity and turns grainy when folded into the chocolate base.
Jane says
Outstanding recipe. Made it for a special birthday and everyone raved about it. Possibly the best cake I ever made?? If you love chocolate, you will love this mousse cake!
Thank You for the recipe!
Jane says
Rave reviews from the birthday crowd. Excellent step by step instructions for us newbies. Thank you for the recipe!
Miranda says
Made this cake and it’s a 100/10