Step 1

Preheat the oven to 150ºC.

Step 2

Combine the water and both sugars in a small saucepan. Bring it to the boil over a high heat to dissolve the sugars. Cube the butter and add it to the pan. Let it melt in the hot liquid. Chop up the chocolate and tip it into a mixing bowl. Pour over the hot sugar mixture and leave for 5 minutes, then stir until the chocolate melts and everything is combined. Leave the chocolate to cool a little while you beat the eggs in another bowl, then pour them into the chocolate mix while stirring. Continue to stir until smooth and combined.

Step 3

Line a 22cm round springform cake tin with greaseproof paper, then wrap the base tightly in foil to ensure that it's sealed. Pour in the mixture. Place the tin into a roasting tray and fill halfway with water. Cook in the oven for 30 minutes, then cool in the fridge for a few hours, until set.

Step 4

For the middle layer, bloom the gelatine in the water for 5 minutes. Pour the 240ml double cream into a medium saucepan and bring to a simmer over a medium heat. Chop the dark chocolate and tip it into a mixing bowl. Chop the white chocolate and tip it into another mixing bowl. Remove the cream from the heat and stir in the gelatine. Divide the hot cream between the two bowls of chocolate and let it sit for a few minutes before stirring everything together. Microwave for 10-20 seconds if the chocolate has not fully melted.

Step 5

In another mixing bowl, whisk the remaining 480ml of cream to soft peaks. Divide a third of the cream between the two chocolate mixtures and fold it in. Divide the remaining cream between the two chocolate mixtures and carefully fold it in. Pour the dark chocolate mousse over the cooled chocolate cake, make sure it's neat and level and chill in the fridge for 30 minutes.

Step 6

Remove the chilled mousse cake and carefully pour over the white chocolate mousse. Chill for another 2 hours. When ready to serve remove the cake from the fridge and grate over the dark chocolate. Slice and enjoy! Serves 8