crosswise Salt Freshly ground pepper Preheat oven to 350 degrees F. Line cookie sheet with buttered foil. Melt butter in heavy large skillet over medium heat. Add mushrooms and saute until tender, about 10 minutes. Add Parmesan and basil. Arrange half of potato slices in solid 9-inch round on buttered foil, overlapping slices. Cover with mushroom mixture, pressing flat as possible. Season with salt and pepper. Top with another layer of potato slices. Cover with buttered foil and another cookie sheet. Place brick atop cookie sheet. Bake until potatoes are tender, about 1 hour 10 minutes. Cool, leaving brick and cookie sheet in place. (Can be made 2 hours ahead. Store at room temperature.) Preheat broiler. Remove brick, top cookie sheet and top piece of foil. Broil galette until crisp and brown, about 2 minutes per side. Cut into 6 wedges.