1½ tsp baking powder
1½ tsp bicarbonate of soda
350g/12½oz caster sugar
85g/3oz cocoa powder
225g/8oz plain flour
2 tsp vanilla extract
125ml/4½fl oz vegetable oil
200g/7oz plain chocolate, broken into pieces
200ml/7fl oz double cream
2 free-range eggs
250ml/9fl oz milk