Peel potatoes and slice very thinly. (We use the slicing side of a grater.) In a shallow baking dish, place one layer of potatoes. Cover with sliced onion, American cheese slices and salt and pepper. Repeat layers of potatoes, onion, and cheese, until the dish is nearly filled. Add milk, filling this dish to about 1-inch deep. Microwave, uncovered, until finished cheese is melted and potatoes are cooked through. This takes a while. I usually cook in five minute increments. Check doneness, and then cook more if needed.
