Makes 12

• 300g butter, softened
• 220g caster sugar
• 375g plain flour
• 5 tbsp cocoa powder
• ½ tsp bicarbonate of soda

1. Preheat the oven to 180C. Line a square tin with baking parchment.
2. In large bowl, beat the butter and sugar until pale and fluffy.
3. Sift in the flour, cocoa powder and bicarbonate of soda. And mix until just combined.
4. Turn into the tin and press it evenly into the base. Prick all over with a fork.
5. Bake for 25 minutes until firm to the touch. While it is still hot, cut into 12 pieces with a knife. Leave to cool, then, remove from the tin.
6. Drizzle with melted chocolate of your choice, before separating the slices.

I used milk and white chocolate melted and swirled together to drizzle, but this looks effective if you drizzle them separately.