Generously sprinkle flour on worksurface and roll out puff pastry to a 12" square. Place rolled pastry on baking sheet lined with parchment paper (or silicone baking mat). Place in refrigerator while preparing filling.
1 Sheet Puff Pastry, defrosted
Pour macerated apples and raisins into a colander placed over a bowl. Discard the juices.
Sprinkle cornstarch, brown sugar, salt, cinnamon and nutmeg over apples and raisins. Toss to coat fruits evenly.
⅓ Cup Brown Sugar, 2 Tablespoons Corn Starch, ½ teaspoon Salt, 1 teaspoon Ground Cinnamon, ½ teaspoon Nutmeg
Pile the apples and raisins in the center of the puff pastry, leaving about a 2-inch border all around—this edge will be folded over the filling.
Lightly beat an egg, then use a pastry brush to gently coat the exposed puff pastry with the egg wash.
1 Large Egg, lightly beaten
Begin folding pastry over filling (leave a middle opening of at least 2 inches to allow steam to escape. Continue to apply egg wash to pastry to ensure it adheres to itself.
Brush egg wash on exposed pastry. Sprinkle generously with raw sugar.
1 Tablespoon Raw Sugar
Return assembled galette to refrigerator (note - this allows the dough to relax while the oven heats up).
Heat oven to 400℉ (205℃).
Bake for 24 - 28 minutes. Pastry should be a dark golden color.
Let galette cool on pan for 20 minutes and transfer to cooling rack to cool completely.
Enjoy!