Clean the leek, cut in half lengthways and cut into pieces approx. 8 cm long. Then cook for approx. 5 - 10 minutes in boiling salted water. Drain well, then layer in a greased ovenproof dish.
Spread the mushrooms and the ham strips over the leek (or mix with the leek if necessary). Spread the cheese over the leek. Mix the cream with salt, pepper and nutmeg and pour over the leek.
Gratinate in the middle of the oven preheated to 200 ° C for about 30 minutes. Serve hot.