1/2 stick butter
1 sm. onion, chopped
1 lg. can mushrooms
3 c. milk
Salt to taste
12 oz. Velveeta cheese
2 cans tuna, packed in water
1 box frozen peas, thawed
1 lb. thin spaghetti

Melt butter. Add chopped onion and cook until transparent. Add mushrooms and set aside. Melt Velveeta cheese in milk and set aside. Cook spaghetti until almost done. Drain. Add cheese mixture and remaining ingredients. Pour in casserole dish. Top with crushed potato chips, if desired. Bake in oven until hot through.