Double Chocolate Mousse Cake


I wanted to create something a little different for my Grandma’s birthday cake.  Something a little different from what I usually do for birthdays and something that was a bit more challenging.

I had seen something similar in a patisserie shop window without the mirror glaze.  So I found myself taking elements from a few different cake ideas and created on this one.

You do need plenty of time to allow the mousse layers to set and chill overnight and it best eaten on the day the mirror glaze is poured on the cake.

You will need:

Chocolate Genoise Sponge:

  • 3 Eggs
  • 80g Sugar
  • 60g Plain flour – sifted with the cocoa powder
  • 20g Cocoa powder
  • 20g Butter

Dark Chocolate Mousse:

  • 150g Dark cooking chocolate
  • 300ml Double cream

White Chocolate Mousse:

  • 150g White cooking chocolate
  • 300ml Double cream

Mirror Glaze:

  • 100ml Double cream
  • 90g Caster sugar
  • 40g Cocoa powder
  • 150ml Water
  • 2 Leaves of gelatine

Chocolate Curls:

  • 30g Dark Chocolate
  • 30g White Chocolate


  • Begin by making the Genoise sponge:
  • Grease and line a 22cm tin and pre heat the oven to 180degrees.
  • Whisk the eggs and sugar together in a stand mixer (if you have one alternatively a hand held) until this has doubled in volume, this will take between 7-10mins on a high speed.
  • Using a spatula, fold in the sifted flour and cocoa powder a spoonful at a time, taking care not to knock out the air you have just whisked into the eggs.
  • Melt the butter then gradually add this by pouring it down the side of the bowl, again fold this in to the cake mixture carefully so you don’t knock out the air.
  • Pour into your prepared tin and cook for 15-20mins (check after 15mins).
  • To ensure this cake is cooked you can insert a cocktail stick into the centre – if it comes out clean it is cooked!
  • Allow to cool in the tin. Then turn out on to a cooling rake to cool completely.
  • Once completely cooled, cut the cake into two rounds by cutting in half horizontally.
  • Prepare a 22cm spring form tin by placing a 20cm diameter thin cake board in the centre. This will help keep the cake stable when removing from the tin later!
  • Trim 1cm off all around the perimeter of the two cake sponges and place one in the tin on top of the board. Put the other cake round to one side.

Next make the dark chocolate mousse layer:

  • Melt the dark chocolate over a bain-marie.
  • Whisk the double cream until thickened but not stiff.
  • With the whisk still running pour in the melted chocolate and continue whisking until totally incorporated.
  • Spoon this into the tin over the sponge making sure the mousse goes around the edges of the sponge so this will be hidden when served.
  • Chill in the fridge for 2-3 hours, this layer should ‘set’ quite quickly.

The white chocolate mousse layer:

  • Melt the white chocolate over a bain-marie.
  • Whisk the double cream until thickened but not stiff.
  • With the whisk still running pour in the melted chocolate and continue whisking until totally incorporated.
  • Remove the cake tin from the fridge. Place the spare cake round in the centre of the set dark chocolate mousse.
  • Gently spoon the white chocolate mousse over the sponge taking care to the mousse goes all around the edges to meet the dark chocolate.
  • The white chocolate mousse will be softer and will take longer to set firm.
  • I left mine over night to set in the fridge. You will need to chill the mousse cake for at least 6 hours.

Mirror glaze:

  • Heat all the ingredients except the gelatine leaves in a pan over a low heat until the sugar has dissolved, whilst stirring constantly.
  • Turn the heat up and bring to the boil and simmer for 2 minutes. Stir gently throughout.
  • Remove from the heat and cool for 10 – 15mins.
  • Soak the gelatine leaves in cold water for at least 5mins. Squeeze out the excess water and stir into the glaze until dissolved.
  • Pass through a fine sieve into a jug to remove any lumps and to ensure a smooth finish.
  • Remove the cake from the fridge place on a cooling rack with a baking try underneath to catch the excess glaze.
  • Pour the glaze slowly and steady to cover all of the cake, checking to make sure you have an even coverage (including the back!).
  • Once the cake has finished dripping, transfer to the fridge to set.

The chocolate curls:

  • Melt each of the chocolates separately over a bain-marie. Pour the melted chocolate on to a non-porous surface; I used the back of glass dish/plate, if you have a marble chopping board that would be perfect.  Chill in the fridge until firm.
  • Hold a sharp knife at 90degree angle and scrape the knife over the chocolate towards you. You will get a curl of chocolate in front of the knife. Store them in and air tight container and keep in the fridge until you are ready to use them.  Repeat this process until all the chocolate has been used or until you have used up both chocolates.

Just before serving sprinkle the chocolate curls over the cake.

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