Spread one slice of bread with the marshmallow creme and the other with peanut butter. Place slices of bananas on both slices of bread, then hold a slice in each hand and bring them together to make a sandwich.
Set the sandwich on the work surface and butter the top with 1 tablespoon butter.
Set the sandwich, butter-side down, in the waffle maker. Spread the remaining butter on top of the sandwich and close the waffle maker.
Toast until golden and crisp, 2 1/2 to 3 minutes.
Remove, slice in half and serve with potato chips.