Preheat oven to 350 degrees.

Cook sausage in skillet until browned. Drain. Cook and drain macaroni as directed on package. Combine milk, cheese and mustard in saucepan and cook over low heat until cheese melts and mixture is smooth. Stir in sausage, tomatoes, mushrooms, green onions and cayenne pepper. Remove from heat and combine with macaroni tossing until well coated. Spoon into a greased 2-quart casserole. Cover and bake 15 to 20 minutes. Stir, sprinkle with parmesan cheese. Bake uncovered for an additional 5 minutes.

Let stand for 10 minutes before serving.