Saw my sister-in-law make these for Easter dinner, and they steal the show every time. Just 4 ingredients!

Remove the foil and continue baking, uncovered, for another 15 to 20 minutes, or until the potatoes are completely tender and the cheese around the edges is deeply golden and crisp. Ovens vary, so keep an eye on them toward the end.
Let the potato stacks rest in the pan for about 5 minutes after you take them out of the oven. Run a small knife around the edges of each cup to loosen, then gently lift the stacks out with a spoon or offset spatula and arrange them on a white serving platter.
Serve the cheesy potato stacks hot, while the edges are still crisp and the cheese is melty. Any that cool down can be rewarmed in the oven at 350°F for about 5 to 10 minutes to bring back a bit of their crunch.