Gratin of Cauliflower with Prosciutto

• 1 large cauliflower

Melt the butter, add the flour and stir in well, add the warmed milk, slowly stirring all the time to avoid lumps. Cook for 5 minutes, still stirring, then add the nutmeg, Parmesan, Parma ham, salt and pepper, stir in well and remove from the heat.

Cut the cauliflower into quarters, boil in salted water until cooked, and drain. Put in a gratin dish, pour over the sauce, sprinkle with mo