600g/1lb 5oz caster sugar
150g/5½oz cocoa powder
750g/1lb 10oz icing sugar
450g/1lb self-raising flour
1 tsp vanilla extract
150g/5½oz dark chocolate, melted
150g/5½oz white chocolate, melted
400g/14oz white chocolate
600g/1lb 5oz unsalted butter, plus extra for greasing
300g/10½oz unsalted butter, softened at room temperature
400ml/13fl oz double cream
12 free-range eggs