Grease a baking dish and place the slices in flakes. Sprinkle with salt and pepper. Mix the processed cheese with the cream and milk. Season with a pinch of salt and nutmeg. Pour over the potatoes. Put the butter flakes on top and sprinkle with grated cheese.
Cover with aluminum foil and cook in the oven at 220 degrees for about 60 minutes. Shortly before the end of cooking, remove the foil and let the gratin brown.
Serve sprinkled with parsley.
If you like, you can also add chopped garlic to the gratin.