Preheat the oven: Set to 400°F (200°C). Line a large baking sheet with parchment paper.

Prep the apples: Peel (optional), core, and thinly slice the apples. Aim for 1/8–1/4-inch slices so they cook evenly.

Mix the filling: In a bowl, toss apples with granulated sugar, brown sugar, cinnamon, nutmeg, lemon juice, vanilla, and cornstarch until evenly coated.

Roll the dough: On a lightly floured surface, roll the pie crust to about 12 inches wide. Transfer it to the prepared baking sheet.

Assemble: Arrange apples in the center, leaving a 2-inch border. You can fan them neatly or pile them rustically. Dot the apples with the butter pieces.

Fold the edges: Gently fold the dough over the apples, pleating as you go. Leave the center exposed.

Finish the crust: Brush the dough with egg wash. Sprinkle the crust with coarse sugar and the exposed apples with the remaining 1 teaspoon granulated sugar.

Bake: Bake for 30–40 minutes, until the crust is deep golden and the apples are tender and bubbling.

Cool slightly: Let the galette rest for 10–15 minutes so the juices set. Slice and serve warm or at room temperature.

Optional serving: Add a scoop of vanilla ice cream or a dollop of whipped cream.