Brown meat and onion with garlic salt until tender in skillet on top of stove. Cook macaroni according to package directions, drain and set aside. Drain hamburger mixture and stir in soup, cream, seasonings, and mushrooms, sour cream and mayo. Layer half of hamburger, macaroni and cheese in a 2 quart casserole. Repeat with meat and macaroni. Save last half of cheese. Bake in preheated 350 degree oven for 20 minutes. Sprinkle with remaining cheese. Return to oven until cheese melts. Makes 6 to 8 servings. Delicious!!!