100 g/4 oz/1 cup plain (semi-sweet)
Melt the butter or margarine and syrup,
then remove from the heat and stir in the cocoa and crushed biscuits.
Spread the mixture in a 23 cm/9 in square cake tin (pan) and level the
surface. Melt the chocolate in a heatproof bowl over a pan of gently
simmering water and spread over the top. Leave to cool slightly, then
cut into bars or squares and chill until set.