Preheat oven to 375°F. Butter 13x9x2-inch glass baking dish. Whisk cream, shallots, rosemary, salt and pepper in medium bowl to blend. Place half of potatoes in prepared baking dish, overlapping slightly. Sprinkle with 3/4 cup cheese. Top with second layer of potatoes. Pour cream mixture over potatoes in dish. Sprinkle with remaining cheese. Cover gratin with foil and bake 1 hour. Uncover and bake until top is golden brown and potatoes are tender, about 45 minutes longer. Let gratin cool 10 minutes before serving.
