In a large bowl, rub the flour and the butter together with your fingertips until you have a breadcrumb texture.

Add the sugar in and mix through. Add cornflour too if using (or sub extra flour).

Still using your fingertips, gently press the dough together until it forms into a ball. There should be enough moisture to do this without adding any liquid.

Divide the dough roughly in half (approx 200g).

Add the cocoa to one half and a bit of extra sugar if required (taste and add). Add the vanilla to the other half and mix through.

Divide each flavour into four balls, then stretch into a long rope. Lay one of each flavour next to each other then twist together.

Coil the two-tone ropes into your greased tin/dish and then gently press together so there are no gaps showing. Score the top in a pattern if you wish, otherwise leave as it is.

Bake at Gas 4 (350f / 180c) for 30-40 minutes. The length of cooking will depend on your dish size and material. The shortbread will start to brown and pull away from the sides of the dish.

Remove from oven and carefully cut into slices whilst still warm (take care if using a non-stick pan). Sprinkle with extra sugar if desired. Leave to cool in the tin before removing.

Enjoy!