150²µ/5½´Ç³ú plain flour
2 tsp baking powder
175g/6oz caster sugar
25g/1oz cocoa powder
4 tbsp cocoa powder
300²µ/10½´Ç³ú icing sugar, sifted
2 tsp vanilla extract
175g/6oz butter, softened
3 large free-range eggs
175g/6oz margarine suitable for baking
2 tbsp full-fat milk
1 tbsp milk, plus extra if needed