Make the Flaky Pastry Dough: In a large bowl, whisk together flour, sugar, and salt. Cut in the cold cubed butter using a pastry cutter or fingertips until pea-sized butter pockets remain. Drizzle ice water 1 tablespoon at a time, tossing gently with a fork until the dough just clusters together. Gather into a round disk, wrap in plastic, and chill for 45 minutes.

Prepare the Spiced Apple Filling: In a medium mixing bowl, gently toss the thinly sliced Honeycrisp and Granny Smith apples with brown sugar, cornstarch, ground cinnamon, nutmeg, vanilla extract, and fresh lemon juice until uniformly coated.

Roll & Assemble: Preheat oven to 400°F (200°C). On a lightly floured piece of parchment paper, roll the chilled dough into a 12-inch rustic circle (roughly 1/8-inch thick). Transfer parchment paper onto a rimmed baking sheet. Arrange apple slices in tight concentric circles, leaving a 2-inch border of bare dough around the edges. Scatter the small butter dots over the apples.

Fold, Pleat & Chill: Gently fold the bare dough border up and inward over the apples, pleating the pastry every 2 to 3 inches to seal. Brush the pleated crust edges generously with egg wash, then sprinkle with coarse turbinado raw sugar. Chill the assembled galette in the freezer for 15 minutes before baking.

Bake to Golden Perfection: Bake at 400°F (200°C) for 38 to 42 minutes until the crust is deep golden brown and crisp, and the spiced apple filling is bubbling in the center.

Caramel Drizzle & Serve: Let cool on the baking sheet for 15 minutes. Generously drizzle warm salted caramel sauce over the warm apples, sprinkle with coarse Maldon sea salt flakes, slice into generous wedges, and serve warm with velvety vanilla bean ice cream!