For enough to last less greedy families than mine you’ll need:
16oz/400g Plain flour
All you need do is to melt the margarine and add the vanilla extract to it. Sieve all the other ingredients into a bowl and mix them up. Mix the melted margarine into this. When you do this you’ll be convinced that it’ll never mix and there’s far too much flour and cocoa and that I’m a fool. Just keep on going and soon it’ll look like the above.
Put this into a tin, brush the top with water and then sprinkle with sugar – this gives it a nice crust on top. Bake at about 150C for 15-20 minutes or until firm when pressed.