Step 1: Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper.
Step 2: In a medium bowl, combine the thinly sliced apples, granulated sugar, ground cinnamon, and all-purpose flour. Toss gently until the apples are evenly coated.
Step 3: Unfold the thawed puff pastry sheet on a lightly floured surface. Cut the pastry into four equal squares.
Step 4: Place a generous spoonful of the apple mixture onto one half of each puff pastry square, leaving a small border around the edges. Drizzle about a tablespoon of caramel sauce over the apples.
Step 5: Fold the other half of the puff pastry over the apple mixture, creating a pocket. Seal the edges firmly by pressing them down with a fork. Using a sharp knife, cut 2-3 small slits on top of each pastry to allow steam to escape.
Step 6: Carefully transfer the assembled pastries to your prepared baking sheet. Brush the tops of the pastries with the whisked egg wash for a beautiful golden sheen, and if desired, sprinkle with coarse sugar.
Step 7: Bake for 18-22 minutes, or until the pastries are puffed up, golden brown, and the filling is bubbling. Baking times may vary depending on your oven.
Step 8: Remove from the oven and let cool slightly on a wire rack. For an extra touch of indulgence, drizzle with more caramel sauce just before serving warm.