1/4 c. chopped onion
1 tbsp. butter
1 can cream of mushroom soup
1/2 c. milk
1/2 c. shredded processed cheese
1/8 tsp. dry mustard
1 (7 oz) can tuna, drained & flaked
2 c. cooked elbow macaroni
1/2 c. cooked peas
1/2 c. potato chips (opt.)

Cook onions in butter until tender. Blend in soup, milk, cheese and seasoning. Heat until cheese melts. Combine with tuna, macaroni and peas. Pour into 1 1/2 quart casserole. Crumble chips on top. Bake at 350 degrees for 30 to 40 minutes.