1. In a deep, 3-quart, heat-resistant, non-metallic casserole place 5 cups water, 1 tablespoon salt and 3 cups uncooked noodles. Heat, covered, in Microwave Oven 12 minutes or until noodles are tender, Stir occasionally. 2. Drain noodles and set aside. 3. In a large, heat-resistant, non-metallic mixing bowl, me1t 1/4 cup butter or margarine in Microwave Oven 30 seconds. 4. Add bread crumbs and heat, uncovered, in Microwave Oven 1 1/2 minutes or until bread crumbs are golden brown. 5. Add meat to bread crumb mixture and mix to combine well. Heat, uncovered, 5 minutes or until meat is browned, stirring occasionally so meat crumbles. 6. Add onions, green pepper, garlic salt, salt and pepper. Blend into meat mixture thoroughly. Heat, uncovered, in Microwave Oven 2 minutes. 7. In a 2-quart, heat-resistant, non-metallic casserole layer cooked noodles with meat mixture. Top with cheese, tomato sauce and mushrooms (in that order). Heat, uncovered, in Microwave Oven 8 minutes or until cheese melts.