Spray a 9 x 13 pan with non-stick cooking spray
Layer:
1 can of potatoes
Slices of butter
1 can of potatoes
Slices of Butter
Pineapple
Syrup/
Hand-mash all ingredients in the pan with a potato masher.
Bake it at 325° uncovered for 45 minutes.
Top with marshmallows. Return to the oven for 5 minutes or until marshmallows are browned and puffy.