Tuna Straw Casserole

1 can tuna, drained 1 can cream of mushroom soup 6 oz.can evaporated milk 4 oz. can broiled sliced mushrooms, drained 1/4 c. pimentoes 4 oz. can shoestring potatoes
Reserve 1 c. potatoes for topping. Combine remaining ingredients and pour into 1 1/2 qt. casserole. Arrange reserved potatoes over top. Cook at 350 25 minutes.