175g/6oz plain flour
1 tsp baking powder
325g/12oz caster sugar
85g/3oz milk chocolate, cut into large chunks
85g/3oz pecans, broken into pieces
1 tsp vanilla extract
275g/10oz dark chocolate (70% cocoa solids)
85g/3oz white chocolate, cut into large chunks
275g/10oz unsalted butter
4 large eggs, lightly beaten