Preheat oven to 350°F. Line a large baking sheet with parchment paper.
In a medium bowl, toss together apples, raisins, sugar, flour, cinnamon, ginger, nutmeg, and kosher salt.
On a lightly floured surface, roll dough into a 14x12-inch rectangle. Carefully transfer the dough to the prepared pan. Smooth or lightly reroll the dough on the pan, if necessary.
Spoon the apple mixture lengthwise down the center of the dough. Cut 1-inch slits in the dough down both sides of the apple mixture, stopping ½ inch from the mixture. Alternately fold the dough strips over the apples. Brush the dough with the egg wash; sprinkle with sparkling sugar.
Bake until the apples are tender and the dough is puffed and golden brown, about 40 minutes. Let the strudel cool on the pan for at least 30 minutes before slicing and serving.
Notes
Remember to thaw the puff pastry according to the package directions before assembling the strudel.
Slice the apples about ¼-inch thick. Keeping the apple slices uniform ensures that they bake evenly and are all soft by the time the strudel is done.
You do not need to peel the apples, although you can if you prefer.
Enjoy leftover apple strudel for breakfast or brunch with a hot cup of coffee!