makes 6-8 servings
3 tablespoons unsalted butter, divided
3 pounds Gala or Fuji apples (about 6), peeled, cored, and thinly sliced
1/2 cup granulated sugar
1 teaspoon ground cinnamon
1/4 teaspoon ground ginger
1/4 teaspoon ground nutmeg
1 sheet puff pastry (from a 17.3-ounce package), thawed
1 tablespoon sanding sugar
1. Melt 2 tablespoons butter over medium heat in a large skillet. Add the sliced apples, sugar, cinnamon, ginger, and nutmeg. Stir to combine, Increase the heat to medium-high and cook, stirring occasionally, until the apples are tender and the liquid has cooked off, 15-20 minutes. Spread the apple filling on a rimmed baking sheet lined with parchment paper and let cool completely. (You can make the apple filling up to a day in advance; refrigerate the apples overnight in an airtight container.)
3. Preheat the oven to 400 degrees. Line a baking sheet with parchment paper and set aside. Lightly flour a work surface and carefully unfold the sheet of puff pastry. Roll the sheet out into a 12x14-inch rectangle.
4. Melt 1 tablespoon of butter and set aside. With the short side of the dough facing you, mound the apple filling in a horizontal strip down the center of the rectangle, leaving a 1-inch border on the short ends. Fold the sides over the apple filling, and carefully turn the pastry over, placing it seam-side down on the prepped baking sheet. Carefully fold under the ends.
5. Brush the pastry with the melted butter and sprinkle with 1 tablespoon sanding sugar. Use a sharp paring knife to cut diagonal steam vents along the center of the pastry. Bake for 35-40 minutes, or until the pastry is golden brown. Let cool on a wire rack for 10 minutes before serving.