Tuna noodle casserole was a household name in the 1950's. Canned tuna would be mixed with egg noodles, peas, cream of mushroom soup, and topped fried onions. This recipe has all those nostalgic flavors but without the use of convenience foods. Celery and mushrooms are sauteed until tender and flour and milk are added to make a roux, a thickening agent for sauces. Frozen peas, canned tuna, and cooked egg noodles are added and the mixture is placed into a baking dish and topped with breadcrumbs. Tuna noodle casserole is a blast from past but still comforting to eat as ever.