275²µ/9¾´Ç³ú plain flour
¾ tsp bicarbonate of soda
200g/7oz light brown sugar
50²µ/1¾´Ç³ú caster sugar
40²µ/1½´Ç³ú cocoa powder
½ tsp flaked sea salt
½ tsp vanilla extract
85g/3oz dark chocolate (60–70% cocoa solids), finely chopped
250g/9oz dark chocolate (60–70% cocoa solids)
200g/7oz unsalted butter, softened and diced