Preheat the oven to 400 degrees F (200 degrees C). Line a large rimmed baking sheet with parchment paper.

Place shredded and chopped apples in a large bowl. Stir in brown sugar, golden raisins, flour, and salt; set aside.

Working with one sheet at a time, place puff pastry on a lightly floured work surface. Roll lightly with a rolling pin into an approximately 10 x 12-inch rectangle. Arrange 1/2 of the apple filling (about 3 cups) down one side of the pastry lengthwise.

Fold pastry lengthwise over apple mixture; dampen edges of pastry with water, then press or crimp edges to seal. Repeat process with the second pastry sheet and remaining apple mixture.

Transfer to prepared baking sheet, leaving at least 2 inches between each pastry. Whisk egg and milk together in a small bowl; brush on top of each pastry. Cut 3 or 4 slits on top of each pastry to allow steam to escape.

Bake in the preheated oven until golden brown, 30 to 35 minutes.