Name: Mary Berry Chocolate Mousse Cake Recipe
Prep time: 30 min
Cook time: 25 min
Total time: 4 h
Ingredients: 150g plain flour; 30g good-quality cocoa powder; 1 tsp baking powder; half a tsp bicarbonate of soda; pinch of fine sea salt; 150g caster sugar; 2 large eggs, at room temperature; 120ml whole milk; 80ml sunflower oil; 1 tsp vanilla extract; 80ml hot strong black coffee; 200g dark chocolate (70% cocoa solids), broken into pieces; 30g unsalted butter, cut into cubes; 3 large eggs, separated; 2 tbsp caster sugar; 200ml double cream, chilled; cocoa powder or finely grated dark chocolate, for dusting

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This chocolate mousse cake is a striking layered dessert with a dense, fudgy sponge base topped by a cloud-light chocolate mousse that sets firm enough to slice cleanly, yet melts into a silky, bittersweet finish on the tongue. It is the kind of showstopper that looks elaborate but comes together with straightforward steps and no specialist equipment beyond a springform tin. Equally suited to a birthday table or a quiet Sunday dinner, it delivers consistent results every time. From start to finish, including chilling time, it is ready in around 4 hours.

What sets this Mary Berry chocolate mousse cake apart is the balance between the two layers. The sponge is dark and moist without being overly sweet, and the mousse above it is airy but stable, holding its shape neatly when the tin is removed. Together they create a contrast of textures that makes each slice feel considered rather than heavy.

Ingredients

For the chocolate sponge base

150g plain flour
30g good-quality cocoa powder
1 tsp baking powder
half a tsp bicarbonate of soda
pinch of fine sea salt
150g caster sugar
2 large eggs, at room temperature
120ml whole milk
80ml sunflower oil
1 tsp vanilla extract
80ml hot strong black coffee

For the chocolate mousse

200g dark chocolate (70% cocoa solids), broken into pieces
30g unsalted butter, cut into cubes
3 large eggs, separated
2 tbsp caster sugar
200ml double cream, chilled

To finish

cocoa powder or finely grated dark chocolate, for dusting

How to Make Mary Berry Chocolate Mousse Cake

Prepare the tin and oven: Heat the oven to 180C (160C fan, gas mark 4). Grease a 20cm springform tin and line the base and sides with baking parchment.
Mix the dry ingredients: Sift the flour, cocoa powder, baking powder, bicarbonate of soda, and salt into a large bowl. Stir in the caster sugar and make a well in the centre.
Combine the wet ingredients: In a jug, whisk together the eggs, milk, sunflower oil, and vanilla extract until combined. Pour this mixture into the well of the dry ingredients and stir until a smooth batter forms. Add the hot coffee and stir again until fully incorporated. The batter will be quite thin, which is correct.
Bake the sponge: Pour the batter into the prepared tin and bake on the middle shelf for 22 to 25 minutes, until the sponge has risen and a skewer inserted in the centre comes out with just a few moist crumbs. Do not overbake, as the sponge needs to remain slightly fudgy.
Cool the sponge in the tin: Leave the sponge to cool completely in the tin before adding the mousse layer, as any warmth will cause the mousse to melt and lose its set. This takes roughly 1 hour.
Melt the chocolate: Place the dark chocolate and butter in a heatproof bowl set over a pan of barely simmering water, making sure the base of the bowl does not touch the water. Stir occasionally until fully melted and glossy. Remove from the heat and leave to cool for 10 minutes.
Add the egg yolks: Beat the egg yolks and caster sugar together briefly, then stir into the cooled chocolate mixture. The sugar helps the yolks blend smoothly without scrambling.
Whip the cream and whites separately: In one bowl, whip the chilled double cream to soft peaks. In a separate, clean bowl, whisk the egg whites to stiff peaks. Both need to be done separately to maintain the right volume in each.
Fold together the mousse: Fold the whipped cream into the chocolate mixture gently using a large metal spoon. Then add the egg whites in two batches, folding carefully until no white streaks remain. The mixture should look pale brown and hold soft, airy peaks.
Set the mousse layer and chill: Spoon the mousse evenly over the cooled sponge base, smooth the top with a palette knife, and refrigerate for a minimum of 2 hours until fully set and firm to the touch. Before serving, dust the surface lightly with cocoa powder or finely grated dark chocolate.

Tips for the Best Mary Berry Chocolate Mousse Cake

Why has my mousse layer not set properly after chilling?

The most common reason is that the chocolate was still too warm when the cream and egg whites were folded in, causing the fat to coat the air bubbles and prevent them from holding. Always allow the melted chocolate mixture to cool to roughly room temperature, around 30 to 35C, before folding.

How do I stop the mousse from going grainy when I fold it?

Graininess usually happens when the egg whites are overwhipped to stiff, dry peaks before folding. Aim for peaks that are firm but still have a slight sheen and curl at the tip rather than standing completely rigid.

Why did my sponge base come out dry instead of fudgy?

A dry sponge base is nearly always the result of a few extra minutes in the oven. Check it at 22 minutes and remove it as soon as the skewer shows moist crumbs rather than clean. The sponge continues to firm up as it cools.

My mousse has a few lumps of chocolate running through it. What went wrong?

This happens when the melted chocolate seizes as it meets the cooler cream or egg whites. Make sure the chocolate mixture is at room temperature before folding, and that the cream is not ice cold straight from the fridge. Take the cream out for 10 minutes before whipping.

How do I get clean slices when cutting the cake?

Run a sharp knife under very hot water, wipe it dry, and cut in one smooth downward motion without sawing back and forth. Repeat the hot water and wipe between every slice for neat, sharp edges through the mousse layer.

Serving Suggestions

Serve each slice with a small pour of lightly whipped double cream alongside, which cuts through the richness of the mousse.
Pair with a shot of strong espresso or an Americano for an after-dinner dessert pairing that brings out the dark chocolate flavour.
Arrange fresh raspberries around the base of each slice for a sharp, fruity contrast to the bittersweet mousse.
Dust the top generously with cocoa powder just before bringing to the table for a polished, restaurant-style finish.
For a dinner party, remove the tin and plate the whole cake on a dark or slate-grey board to let the glossy mousse layer show clearly.

Storage

Room Temperature

The chocolate mousse cake is not suitable for storing at room temperature once assembled due to the raw egg whites and cream in the mousse layer.

Refrigerator

Store the cake, loosely covered with cling film or in an airtight container, in the refrigerator for up to 3 days. Remove it from the fridge 15 to 20 minutes before serving so the sponge base softens slightly and the mousse loses its fridge-cold firmness.

Freezing

Freeze individual slices by wrapping each one tightly in cling film and placing in a freezer-safe container for up to 6 weeks. Defrost overnight in the refrigerator and allow to sit at room temperature for 15 minutes before serving, as freezing can slightly alter the texture of the mousse layer.

Nutrition

Calories: 420 kcal
Carbohydrates: 38g
Protein: 7g
Fat: 27g
Saturated Fat: 14g
Sodium: 180mg

Nutrition values are estimates based on standard ingredient weights and may vary depending on the brands and specific ingredients used, as well as the slice size.

FAQs

Can I use milk chocolate instead of dark chocolate for the mousse?

Yes, milk chocolate works but the mousse will be noticeably sweeter and slightly softer in texture when set. Reduce the caster sugar in the mousse to 1 tablespoon to compensate, and allow an extra 30 minutes of chilling time as milk chocolate sets less firmly than dark.

Can I make this chocolate mousse cake the day before serving?

Yes, and in fact it benefits from being made ahead. Making it the evening before gives the mousse a full overnight chill, which results in a firmer, cleaner slice. Keep it covered in the fridge and dust with cocoa powder just before serving.

What size springform tin works best for this recipe?

A 20cm springform tin gives the best proportion of sponge to mousse, producing a generous mousse layer of around 4 to 5cm. A 23cm tin can be used but will give a shallower result, and the sponge will bake in around 18 to 20 minutes rather than 22 to 25.

Can I make this recipe gluten-free?

The sponge base can be made gluten-free by swapping the plain flour for a good-quality gluten-free plain flour blend at the same weight. The mousse layer is naturally gluten-free. Check that your baking powder is also labelled gluten-free, as some brands use a wheat-based carrier.

Can I add a flavouring to the mousse, such as orange or coffee?

Both work well. For an orange flavour, stir the finely grated zest of one orange into the melted chocolate mixture before folding. For a coffee variation, dissolve 1 teaspoon of instant espresso powder in a teaspoon of warm water and add it with the egg yolks. Neither addition affects the set of the mousse.

Conclusion

This Mary Berry chocolate mousse cake brings together a tender, cocoa-dark sponge and a light, billowy mousse into one elegant dessert that slices cleanly and holds its shape beautifully on the plate. The recipe is manageable for a capable home baker and produces 8 generous slices, making it ideal for gatherings where you need something that looks impressive but does not require advanced technique. The combination of textures, dense sponge meeting airy mousse, is what keeps this recipe worth returning to.

Whether it is for a celebration, a dinner party dessert, or simply a weekend bake for the family, this cake rewards careful temperature control and a little patience during the chilling stage. If you try this recipe, leave a comment below with how it turned out or share it with someone who loves chocolate desserts. If you enjoyed this, you might also like the Mary Berry Chicken Tagine Recipe for a satisfying, reliable main course to pair with a special occasion meal.