Preheat oven to 450°.
Combine salt and pepper in a small bowl.
Melt 2 1/2 tablespoons butter in a 10-inch cast-iron or ovenproof heavy skillet over medium heat. Arrange a single layer of potato slices, slightly overlapping, in a circular pattern in pan; sprinkle with 1/4 teaspoon salt mixture. Drizzle 1/2 teaspoon melted butter over potatoes. Repeat the layers 5 times, ending with butter. Press firmly to pack. Cover and bake at 450° for 20 minutes.
Uncover and bake an additional 25 minutes or until potatoes are golden. Loosen edges of potatoes with a spatula. Place a plate upside down on top of pan; invert potatoes onto plate. Sprinkle with parsley, if desired.