Step 1: 1. grease a 28cm x 18cm slice tray.
Step 3: 2. measure dry ingredients into a mixing bowl.
Step 5: 3. melt margarine over a low heat.
Step 7: 4. pour melted margarine into the dry ingredients with the beaten egg. Mix well.
Step 9: 5. spread mixture over the base of the slice tray.
Step 11: 6. bake in a moderate (1800) for 20 minutes or until just firm to the touch.
Step 13: 7. sift icing mixture and cocoa into a bowl, stir in margarine and milk to give a thick paste.
Step 15: 8. spread with icing as soon as the slice comes out of the oven. Leave slice in the tin.
Step 17: 9. stand in the fridge for 10 minutes before cutting into squares.