Preheat the oven to 160°C fan (180°C conventional). Grease and line an 8-inch square tin.
Beat together the butter and sugar until light and fluffy.
180 grams Unsalted butter or margarine, 180 grams White caster sugar
Add the eggs one at a time, mixing well.
3 medium Eggs
Stir the flour, cocoa and baking powder together. Then add to the mixture with the milk and fold gently until combined.
150 grams Self-raising flour, 30 grams Cocoa powder, 1 teaspoon Baking powder, 2 tablespoon Milk
Spread into the tin and bake for 30 minutes or until a skewer comes out clean.
Leave the cake to cool in the tin for 15 minutes, then lift out and place in the freezer for 45 minutes. Why? This firms up the sponge, making it easier to trim and slice into neat squares without crumbs.