Lickety Split Tuna Casserole

Ingredients

• 1 7.5 oz (ounce) box macaroni and cheese, prepared according to package directions This usually takes 1/4 cup milk and 1/4 cup butter or margarine
• 1 10 oz can condensed cream of mushroom soup (or use another flavor such as celery) plus 1/4 cup milk
• 2 small cans of tuna, drained (or one 12 oz can)
• Dry bread crumbs or cracker crumbs or cornflakes, crushed, plus one Tablespoon butter or margarine for topping (optional)