300g best dark chocolate
50g best milk chocolate
175g unsalted butter
8 large eggs, separated
100g light brown sugar
100g caster sugar
1 tablespoon vanilla extract
pinch of salt
25cm spring form tin foil
Preheat the oven to gas mark 4/180Â°C and put the kettle on to boil.
Line the inside of the springform with foil, making sure you press the foil well into the sides and bottom of the tin to make a smooth surface.
Melt chocolate and butter in a double boiler or microwave, let it cool.
In another bowl beat the egg yolks and sugars until pale and really thick, like mayonnaise.
Whisk the egg whites in a large bowl until soft peaks form then fold gently into the chocolate mixture.
Pour the cake batter into the foil-lined spring form which you have placed in a large roasting tin.
Add the hot water from the kettle to come about half way up the sides of the tin and put into the oven.
Bake for 50 minutes to 1 hour.
The inside of the cake will be damp and mousse-like but the top should look cooked and dry.
Let it cool completely on a cooling rack before releasing from the tin.
Now peel the foil gently away from the sides.