Preheat your oven to 425 degrees F. Line a rimmed baking sheet with parchment paper and set aside.
Add the butter to a large skillet and melt over medium heat. Add the apples, brown sugar, cornstarch, cinnamon, nutmeg, and ginger to the skillet and toss, coating the apples in the butter and spices.
2 tablespoons butter, 3 Honeycrisp apples, peeled, cored, sliced thinly, ⅓ cup brown sugar, 1 tablespoon cornstarch, 1 teaspoon ground cinnamon, ¼ teaspoon nutmeg, 1 pinch ground ginger
Saute the apples for about 5 minutes, stirring every minute or so to cook the apples evenly.
Stir in the raisins and golden raisins then remove the skillet from the heat and set it aside.
¼ cup raisins, ¼ cup golden raisins
Add the egg and heavy cream to a small bowl and whisk together.
1 egg, 1 tablespoon heavy cream
Dust a flat work surface with flour and roll out the puff pastry into a rectangle about 14” wide and 18” long (the size does not have to be exact but you want it to be nice and thin). Move the rolled puff pastry to the prepared sheet tray.
1 sheet frozen puff pastry dough, thawed
Scoop the apple mix onto the puff pastry, piling it down the center of the pastry. Make the filling about 4” wide down the middle of the puff pastry but keep it about 2 inches away from the top and bottom.
Brush the puff pastry that does not have apple filling on it with the egg and cream mix. Then, fold one inch of the top and bottom puff pastry rectangle up over the apple filling, closing up the ends of the strudel.
Fold one side of the puff pastry over the apple filling. Fold the other side over the apple filling and let it overlap the first half.
Roll the strudel over on the tray so the folded seam is on the bottom. Brush the whole pastry with the remaining egg wash.
Score the strudel with a sharp knife, making small slits all the way down.
Sprinkle the strudel with a little sugar then bake for 25 minutes. The strudel will be a light golden brown and look flakey.
Let it cool for about 15 minutes before slicing and serving.