225g/8oz plain flour
陆 tsp baking powder
陆 tsp bicarbonate of soda
100g/3 陆oz soft brown sugar
100驳/3陆辞锄 caster sugar
陆 tsp fine salt
100驳/3陆辞锄 self-raising flour
1 tsp vanilla extract
250g/9oz white chocolate chunks
75驳/2陆辞锄 white chocolate, cut into chunks
200g/7oz unsalted butter, softened
1 free-range egg, plus 1 egg yolk