In skillet cook bacon crisp. Drain, reserve 2 tbsp drippings in skillet. Crumble bacon, set aside. Cook leeks in drippings till tender, drain. Place bacon in pastry shell, top with cheese and leeks. Combine egg and milk, beat in flour, salt, and nutmeg. Pour mixture into shell. Bake in 325 degree oven for 45 minutes, or till nearly set in center. Let cool 10 to 15 minutes before serving. Serves 6.