Preheat oven to 400°F.
Rinse, dry, and thinly slice the potatoes.
Butter a large, shallow ovenproof dish; melt the remaining butter in a small pan. Put a layer of potatoes in the bottom of the dish. Drizzle a little butter over and season lightly with salt and pepper. Repeat these layers, finishing with butter.
Cover and cook in a preheated 400°F oven for 1 hr.
Sprinkle with chopped parsley and serve from the dish.