1. CREAM together butter and sugars until light and fluffy. Whisk in egg and vanilla. Stir in sifted flours and then the chocolate.
2. ROLL a tablespoonful of mixture into a ball and place on a greased baking tray, pressing down slightly. Repeat with remaining mixture, allowing room for spreading.
3. BAKE in a moderate oven 180°C for 15 minutes or until cooked. Cool on a wire rack. Store in an airtight container until required.
4. BEAT the extra butter until pale and creamy. Add the vanilla and milk then gradually beat in the icing sugar until thick and fluffy. Divide and colour the buttercream as desired.
5. SPREAD a thick layer of buttercream onto 16 cookies then lightly sandwich together. Decorate with eyes then allow the buttercream to firm. Store in an airtight container until required.
TIP: Beat in only enough icing sugar to make a thick buttercream icing, you may not require the whole 3 cups.