Step 1: Prepare the Dough : In a large bowl, whisk together flour, sugar, and salt. Cut in cold butter using a pastry cutter or fingers until mixture resembles coarse crumbs. Gradually add ice water, 1 tbsp at a time, until dough comes together. Form into a disc, wrap in plastic, and chill for at least 30 minutes.

Step 2: Prepare the Apple Filling : In a medium bowl, toss apple slices with granulated sugar, brown sugar, cinnamon, nutmeg, lemon juice, vanilla extract, and flour. Set aside.

Step 3: Roll Out Dough : On a lightly floured surface, roll dough into a 12-inch circle about ⅛-inch thick. Transfer dough to a parchment-lined baking sheet.

Step 4: Assemble the Galette : Arrange apple slices in the center of the dough, leaving a 2-inch border. Fold the edges over the apples, pleating gently to create rustic folds. Brush the dough edges with beaten egg and sprinkle with coarse sugar.

Step 5: Bake : Preheat oven to 375°F (190°C). Bake galette for 40–45 minutes, or until crust is golden brown and apples are tender. Remove from oven and let cool slightly on the baking sheet.

Step 6: Serve : Serve warm or at room temperature. Optionally, top with vanilla ice cream or whipped cream for extra indulgence. Slice carefully with a sharp knife or pie server.