1 tsp baking powder
90g/3¼oz light brown sugar
2 tbsp cocoa powder
pinch salt
70g/2½oz self-raising flour
50ml/2fl oz sunflower oil, plus extra for greasing
75g/2â…”oz dark chocolate, broken into pieces
40g/1½oz white chocolate, broken into pieces
3 tbsp double cream
1 large free-range egg
1 tsp espresso coffee powder