1 tsp baking powder
190驳/6戮辞锄 caster sugar
450g/1lb icing sugar
170g/6oz self-raising flour
1 tsp vanilla bean paste or vanilla extract
60g/2录oz cookies and cream biscuits, crushed into crumbs
50g/1戮oz cookies and cream biscuits, crushed into crumbs
120g/4录oz unsalted butter, softened
275g/9戮oz unsalted butter, softened
3 free-range eggs
splash of milk
140g/5oz soured cream (or 5 tbsp milk)