Put 2-3 tablespoons of water into a wide saucepan with the butter and a pinch of salt. Bring to the boil, add the cabbage and toss constantly over a high heat, then cover for a few minutes.

Render down the scraps of fat in a hot, wide saucepan until the fat runs. Discard the pieces. Cut the vegetables into slightly smaller dice and toss them in the fat, leaving them to cook for 3-4 ...