might be this?
Chocolate Concrete...
510g margarine
510g sugar
680g plain flour
55g cocoa
20g baking powder 1 egg (size 4)
pinch of salt
Mix all dry ingredients together. Rub in margarine. Beat the egg and add to the mixture (for best results mix entirely in a food mixer or processor). Knead lightly until mixture blends together. Press into well-greased shallow tins. Bake gently for 25 - 30 minutes Gas mark 4. Do not overbake. Put a lid on the tin and keep hot otherwise crunch will set hard - like concrete!