Cut a round of parchment paper to fit just inside a 12-inch heavy skillet and butter one side.
Slice potatoes 1/8 inch thick with slicer. Arrange in skillet.
Add water, 3/4 teaspoon salt, and 1/2 teaspoon pepper. Dot top with butter. Cover potatoes with parchment, buttered side down, and briskly simmer until tender and most of liquid has evaporated, 30 to 35 minutes.