Cut the cabbage lengthways and soak it in salted water for about 10 minutes to scare away all the small animals. Then wash properly, cut into strips and boil in enough water for about 15 minutes, drain.
Mix the flour in the fat, slowly pour in the milk, stir with a whisk and cook well. Season with salt, pepper and grated nutmeg.
Pour a layer of sauce into a spout that has been spread with fat, pour the cabbage over it, then pour the rest of the sauce over it. Sprinkle with cheese and grill on the lowest rack in the grill.