1. Crush the peppercorns using a mortar and pestle, then mix with the nutmeg. Combine butter with the spices, then chill. You can make the butter 3 days ahead. Store it in the fridge wrapped in cling film.
2. Remove outer leaves and stem from cabbage, then thickly slice. Boil in salted water for 5 mins until just tender. Drain and tip into a serving bowl. Toss with the butter, check the seasoning, then serve.