Anna Louise A chocolate mousse cake is not a conventional cake. It has no flour. It does not rise. When it comes out of the oven it looks undercooked and slightly sunken and that is exactly right — the centre should still have a tremor.
As it cools it sets to something that sits between a baked chocolate mousse and a flourless chocolate cake — intensely dark, barely set in the centre, with a slightly crisp, paper-thin crust on top and a texture that is simultaneously dense and airy.
It is one of the most purely, intensely chocolate things you can eat. It is also one of the most impressive desserts in this repertoire — it looks dramatic on a plate, takes thirty minutes of active work, and causes complete silence at the table when it is first eaten.
This is the dessert for serious chocolate occasions.
Ingredients for Mary Berry Chocolate Mousse Cake
For the Cake
- 300g good quality dark chocolate (70% cocoa solids), finely chopped
- 200g unsalted butter, cut into cubes
- 6 large eggs, separated — yolks and whites in separate bowls
- 200g golden caster sugar — divided: 150g for the yolks, 50g for the whites
- 1 tsp vanilla extract
- 2 tbsp espresso or very strong coffee — cooled to room temperature
- ½ tsp fine salt
To Serve
- Icing sugar for dusting
- Double cream, softly whipped — a generous spoonful per serving
- Fresh raspberries — the sharpness cuts through the richness beautifully
- Crème fraîche if preferred
How to Make Mary Berry Chocolate Mousse Cake
Step 1 — Preheat and Prepare
Preheat your oven to 160°C / 140°C fan / Gas 3. Grease a deep 23cm round springform tin. Line the base with baking parchment. Wrap the outside of the tin with a double layer of foil — this prevents any butter from leaking during baking.
Step 2 — Melt the Chocolate and Butter
Place the chopped chocolate and butter in a large heatproof bowl over barely simmering water. Stir gently until completely smooth and glossy. Remove from the heat and leave to cool for ten minutes — the mixture must be warm but not hot when the eggs go in.
Add the espresso and vanilla extract. Stir to combine.
Step 3 — Beat the Yolks and Sugar
In a large bowl, whisk the egg yolks and 150g of the golden caster sugar together with an electric hand whisk for three to four minutes until very pale, thick, and mousse-like. The mixture should fall from the whisk in thick ribbons.
Fold the cooled chocolate and butter mixture into the beaten yolks gently but thoroughly — the mixture should be smooth, dark, and glossy.
Step 4 — Whisk the Egg Whites
In a perfectly clean bowl — any trace of fat prevents proper whisking — whisk the egg whites with the salt until they reach soft peaks. Add the remaining 50g of caster sugar and whisk to firm, glossy peaks. The whites should hold their shape when the whisk is lifted but not look dry or grainy.
Step 5 — Fold the Whites In
Fold one large spoonful of the whisked whites into the chocolate mixture first — this loosens it and makes folding in the remainder easier without deflating the whites. Then add the remaining whites in two additions, folding gently with a large metal spoon in broad, sweeping motions. Stop the moment no white streaks remain. Every additional fold deflates the mousse.
Step 6 — Bake
Pour the mixture into the prepared tin. Spread gently.
Bake for 28 to 32 minutes. The edges should be set and the top should have formed a thin, slightly crisp, paper-thin crust. The centre should still have a definite wobble when the tin is gently shaken — it should look underdone. This is correct.
Leave to cool completely in the tin on a wire rack — at least two hours. The cake will sink as it cools, developing the characteristic sunken centre that is the hallmark of this dessert.
Step 7 — Release and Serve
Run a palette knife around the edge. Release the springform sides very gently. The cake is fragile. Slide onto a serving plate.
Dust generously with icing sugar. Serve in thin slices — it is rich — with softly whipped cream and fresh raspberries alongside.
My Top Tips For Perfect Chocolate Mousse Cake
Use 70% dark chocolate. This cake has no flour, no rising agent, no sugar beyond what is in the recipe. The chocolate is everything. Good quality 70% gives an intense, complex, slightly bitter flavour. Lower quality chocolate gives something that tastes flat and sweet.
Cool the chocolate before adding the eggs. Even slightly warm chocolate added to egg yolks begins to cook them and gives a grainy, slightly scrambled result. Ten minutes of cooling after melting is the minimum — test it on the back of your wrist.
The egg whites must be in a completely grease-free bowl. Fat prevents egg whites from whisking to full volume. Wipe the bowl and whisk with a piece of kitchen paper dampened with white wine vinegar before using.
The centre wobble is correct. Remove when the centre still wobbles. The residual heat from the tin and the eggs continues to set the centre as the cake cools. A completely set centre in the oven means an overbaked, dry-textured cake when cool.
The sunken centre is correct. The cake sinks as it cools — this is not a problem, it is the characteristic appearance of a chocolate mousse cake. The sunken centre holds the cream and raspberries beautifully when serving.
Serve in thin slices. This cake is extremely rich. A thin slice — perhaps 2cm — is the right portion. It is considerably more satisfying than it looks.
Serving Suggestions
With softly whipped cream and fresh raspberries — the sharpness of the raspberries against the intensely dark cake is the perfect contrast. With crème fraîche for something less sweet. As a dinner party dessert — it is made completely ahead and needs no last-minute work. On a plain white plate where the dark, dramatic cake can speak for itself.
How to Store
In the fridge: Store covered for up to 4 days. The texture becomes even more fudgy and dense on refrigeration. Bring to room temperature for thirty minutes before serving.
In the freezer: Freeze in slices for up to 3 months. Defrost overnight in the fridge and bring to room temperature before serving.
Mary Berry Chocolate Mousse Cake Recipe
Ingredients
Method
- Preheat oven to 160°C / 140°C fan / Gas 3. Grease and line a 23cm springform tin. Wrap outside in double foil.
- Melt chocolate and butter over barely simmering water — stir until smooth. Cool 10 minutes. Add espresso and vanilla.
- Whisk egg yolks and 150g sugar 3–4 minutes until very pale and mousse-like. Fold cooled chocolate mixture in gently until smooth and glossy.
- Whisk egg whites with salt in a clean grease-free bowl to soft peaks. Add 50g sugar — whisk to firm, glossy peaks.
- Fold one large spoonful of whites into chocolate mixture to loosen. Add remaining whites in 2 additions — fold gently in broad sweeping motions until no white streaks remain.
- Pour into tin. Bake 28–32 minutes until edges are set, top has a thin crisp crust, and centre still wobbles when gently shaken. Cool completely in tin — 2 hours. Release gently.
- Dust with icing sugar. Serve in thin slices with whipped cream and raspberries.
Notes
Frequently Asked Questions
Can I add orange zest to the batter?
Yes — the zest of one unwaxed orange added with the espresso gives a chocolate orange version that is completely wonderful.
Can I make this without the espresso?
Yes — replace with one tablespoon of warm water. The espresso does not make the cake taste of coffee — it deepens and intensifies the chocolate flavour. Without it the chocolate flavour is slightly less complex but still very good.
Why is my chocolate mousse cake grainy?
The chocolate was too warm when the eggs were added and partially cooked the yolks. Cool the chocolate more thoroughly before combining with the egg mixture.
Can I make this in a smaller tin?
Yes — a 20cm tin gives a deeper, slightly more dramatic cake. Reduce the baking time to 24 to 28 minutes and check the wobble test carefully.
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