Method

Preheat oven to 160°C.

Cream the butter and sugar until light and fluffy. Stir in sifted flour, cocoa and custard powder until combined. Roll rounded teaspoonfuls of the mixture into balls and place on greased baking trays. Lightly press the top of each with a fork.

Bake in a moderately slow oven (160°C) for 10-15 minutes. Cool on the tray for 10 minutes before lifting off onto a rack to cool completely. Store in an airtight container until required.

Cream together the extra butter, sugar and cocoa to make a smooth icing. Sandwich together pairs of biscuits with icing. Store in an airtight container until required.