Grandma Estee'S Tuna Casserole
["1/4 c. chopped onion", "1 Tbsp. margarine or butter", "2 cans cream of mushroom soup", "1/2 c. shredded processed cheese", "1/8 tsp. dry mustard", "1 (7 oz.) can tuna, drained and flaked", "2 c. cooked macaroni", "1/2 c. cooked peas", "1/2 c. potato chips"]
["In saucepan, cook onion in butter until tender.", "Blend in soup, cheese and seasoning.", "Heat until cheese melts.", "Combine with tuna, macaroni and peas.", "Pour into 1 1/2-quart casserole dish.", "Crumble potato chips on top.", "Bake in moderate oven until nicely browned and bubbling."]
["onion", "margarine", "cream of mushroom soup", "processed cheese", "dry mustard", "tuna", "macaroni", "peas", "potato chips"]