Chocolate concrete

Heat the oven to 180C/160C fan/gas 4. Butter a 20cm x 20cm loose-bottomed square baking tin and line with baking paper. Combine the flour, 225g of the sugar and the cocoa powder in a bowl, then pour over the melted butter and add a pinch of salt, if you like. Stir together using a wooden spoon until the mixture just comes together, then use your hands to lightly knead it until well-combined with no visible flour. Tip the mixture into the tin, then press into a flat, even layer using the back of a spoon.

Bake on the middle shelf of the oven for 20 mins. It will feel soft when baked but will firm up as it cools. Sprinkle over the remaining 1 tbsp of sugar, then leave to cool in the tin for 10 mins before carefully transferring to a wire rack to cool completely. Once cooled, cut into 16 squares.