Preheat the oven to 450°F and line a large, rimmed baking sheet with parchment paper.
Place the squash and onions in a medium bowl and toss with olive oil, salt and peppers. Spread onto a baking sheet and bake for 20 minutes. Remove from the oven and drizzle with maple syrup. Stir to coat and roast for an additional 10 minutes until the squash starts getting tender and caramelized. Remove from the oven and let it cool down.
ASSEMBLE THE STRUDEL:
While the squash is roasting, take the puff pastry out of the freezer and let it thaw out for 20 to 30 minutes.
Unfold both pieces and set them on the prepared baking sheet. Cut the pastry as shown in the step-by-step photos in the post (top corners cut off and notch bottom to create end flaps).
Turn the oven temperature down to 400°F.
Spoon half of the turkey onto each pastry right down the middle portion. Divide the cranberries and sprinkle them on top of the turkey. Spoon on the cooled-down roasted squash and onions (you may have extra that you'll wish to save and nibble on later). Divide the cheese and rosemary and sprinkle those on top of the squash.
Next, you'll braid the pastry. Cut strips on both sides of the filling at a 45° angle (it should be cut parallel to the pieces that you cut off on the top). Fold the top flap over the filling, and then begin braiding the pastry over the filling, one side and then another. Keep going, alternating sides until you get near the bottom. Fold the bottom flap over the filling and finish braiding the rest of the pastry until all strips are folded over.
In a small dish, whisk together egg and water. Brush the egg wash over each of the strudels.
Put the strudels in the oven and bake for 20 to 30 minutes, or until golden. Let cool for 5 minutes before slicing. Each serving is ½ of a strudel. Serve with chunky cranberry sauce for best flavor combination.
Notes
If you have some leftover butternut squash that was already roasted from another recipe, go ahead and use that in place of the maple roasted squash in this recipe.
Experiment with a different cheese if you'd like. The Swiss was a good combo with the ingredients in this recipe.
Serve with chunky cranberry sauce on the side. Top a bite of the strudel with some cranberry sauce and...mmmm.