Cook macaroni in pleanty of salted water until tender,8 to 10 minutes.Drain.In a large casserole,toss macaroni with butter,cayenne and salt and pepper.Mix the milk with the egg and mustard and mix into the macaroni.Toss the two cheeses together and mix half the cheese with the macaroni.Set aside the remaining cheese. Bake in a preheated 350 deg.oven for 10 minutes.Add half of the remaining cheese and mix well.Bake 5 minutes more.Mix in remaining cheese and bake another 10 minutes.Makes 4 servings...