Heat the oven to 180C/160C fan/gas 4. Butter a 30 x 20cm cake tin or deep baking tray and line with baking parchment. Sift the flour and cocoa into a bowl and set aside.

Melt the butter and dark chocolate together in a heatproof bowl set over a pan of simmering water, making sure the bowl doesn’t touch the water. Or, do this in short bursts in the microwave. Once melted, set aside to cool slightly.

Beat the eggs and sugar together in a large bowl using an electric whisk until thick and doubled in volume. (When you lift the beaters, the mixture should leave a trail that lasts 2-3 seconds.) Fold in the melted chocolate mixture followed by the flour mixture, then the grated courgette and milk chocolate chips. Do this gently to retain as much air in the batter as possible.

Tip the batter into the prepared tin, gently level the surface with a spatula or palette knife, and bake for 20-30 mins, or until just set – the top should have a shiny crust, but the centre should have a slight wobble. Leave to cool completely in the tin, about 1 hr. Remove to a board and cut into 16 pieces. Will keep in an airtight container for up to five days.