Rinse and peel your potatoes. With a good sharp knife, cut fairly thin slices (approximately ⅛ of an inch). Lay six pats of butter in the bottom of a pan, and lay in one layer of your potato slices, slightly overlapping them. Lay in another six pats of butter on top of the potatoes, then another layer of potatoes. Repeat until all your pototoes and butter are layered in the pan.
Pop this in the oven, and after an hour and a half or so, you'll have wonderfully delicious crispy potatoes. If you want them crispier, just keep them in the oven longer - up to 2 hours.