Preheat oven to 425*. Wash potatoes well, and cut to 1/4 to 1/2” slices. Lightly spray baking sheet(S) with cooking spray. Melt butter, and brush on both sides of potato slices, and arrange slices on baking sheet(s). Bake, flipping half way through to crisp both sides, for 30 minutes or until fork tender. Remove from oven and sprinkle a bit of crumbled bacon and scallions on top of each potato slice. Top each with a bit of shredded cheddar cheese. Return to oven for 5-10 minutes or until cheese is melted.  Arrange on a platter, and serve with sour cream.