POTATO AND PARMESAN GRATIN

Steps:

• Put oven rack in middle position and preheat oven to 350°F.
• Peel potatoes and cut into 1/8-inch-thick slices with a knife or an adjustable-blade slicer, spreading slices out on a large kitchen towel. Sprinkle with sea salt (1 1/2 teaspoons).
• Stir together cream and milk.
• Dot bottom of a 3-quart shallow baking dish (13 by 9 inches) with half of butter and pour in 1/3 cup cream mixture. Without rinsing or drying potatoes, divide into 5 piles. Layer potatoes in baking dish, 1 pile per layer, spreading 1/3 cup cream mixture and one fourth of cheese between layers. Drizzle remaining cream mixture over potatoes and dot with remaining butter.
• Bake, uncovered, until potatoes are very tender and top is browned, about 2 hours. Let stand at room temperature 10 minutes before serving.