Place potatoes in a pot, cover with water and boil until about 75% cooked through. This will take 15 to 20 minutes, depending on how big the potatoes are.Note: You want to be able to pierce them with a fork but there should still be a little resistence.
While potatoes cook, mix together condensed soup, sour cream, and mayonnaise in a medium bowl. Set aside.
Preheat oven to 350 degrees and spray a 9x13-inch baking dish with cooking spray.
Drain potatoes and let cool for 5 to 10 minutes. Peel skins off and cut into slices.
Arrange half the potato slices in the bottom of the prepared baking dish. Season with salt and pepper.
Arrange half the onion slices and half the ham on top of the potatoes.
Spread half the soup mixture on top and then sprinkle with half the cheddar cheese.
Repeat with another layer of potatoes (season with salt and pepper), onions, ham, soup mixture and the remaining cheddar cheese.
Scatter the butter slivers on top.
Bake for 30 to 40 minutes or until golden.
This recipe originally appeared on spicysouthernkitchen.com