200g/7oz plain flour
Β½ tsp baking powder
1 tsp bicarbonate of soda
175g/6oz light soft brown sugar
75²µ/2ΒΎ΄Η³ϊ caster sugar
40²µ/1Β½΄Η³ϊ cocoa powder
good pinch salt
1 tsp vanilla extract
125²µ/4Β½΄Η³ϊ dark chocolate, chopped
250g/9oz white chocolate, chopped into 1cm/Β½in pieces
175g/6oz unsalted butter, softened
2 free-range eggs, lightly beaten