1 1/2 pound hamburger -- browned, drained
16 ounces shredded Mozzarella cheese -- or more to taste
1 onion -- chopped
1 package sliced pepperoni
2/3 box rigatoni noodles -- cooked
1 can cream of mushroom soup
1 can mushrooms
2 jars pizza sauce

Alternate layers in crockpot as follows; hamburger, noodles, cheese, soup, mushrooms, onions, sauce and pepperoni. Heat 4 hours on LOW in crock pot.