for the biscuits
150g icing sugar
50g cocoa powder
300g plain flour
for the icing
150g butter, or replace 100g butter with 100g peanut butter for a nutty cream!
300g icing sugar, sifted
a couple of drops vanilla extract
For the biscuits, sift the icing sugar, cocoa and flour into a large bowl. Add the butter and using your fingertips, rub the butter into the flour mixture until it resembles fine breadcrumbs. Then using your hands squash together the crumbs together until they come together in a ball. Cut the ball in half and roll each half (on a lightly floured work surface) into a log about 5cm in dia. Wrap in cling film and chill for 30min.
Line 2 baking sheets with baking parchment. Cut the log into 32 rounds, 6mm thick and place on the sheets. Cook at 150°C for 20-25min, then leave to cool for 5min before transferring to a wire rack to cool completely. When cold sandwich two biscuits together with the buttercream.
To make the buttercream, place the butter in a bowl and beat until pale and light, add the icing sugar a spoonful at a time, beating well between additions. Then stir in the milk and vanilla extract.