175g/6oz plain flour
1 tsp bicarbonate of soda
300g/10½oz soft light brown sugar
40²µ/1¾´Ç³ú cocoa powder, plus 2 tbsp
icing sugar, for dusting
pinch salt
1 tsp vanilla extract
175g/6oz unsalted butter, at room temperature, plus extra for greasing the dish
double cream, to serve
3 large free-range eggs, beaten
3 tbsp milk