Cut the cabbage into quarters and remove the thick part of the central stalk. Slice the leaves into strips and cut these across in half, to make them easier to eat. Wash and drain the strips.
Bring a pan of salted water to the boil, drop in the cabbage and boil for 3 minutes for a spring cabbage, 5 minutes for Savoy. Drain well to remove as much water as possible. Dice the potatoes.