In a medium bowl, combine flour and salt. Cut in the cold butter until it resembles coarse crumbs. Gradually add ice water until the dough comes together. Shape into a disk, wrap in plastic, and refrigerate for at least 30 minutes.

Preheat oven to 400°F (200°C). Peel and slice the winter squash into thin wedges. Toss with olive oil, minced garlic, and salt. Spread on a baking sheet lined with parchment. Roast for 20-25 minutes until tender.

Combine roasted squash with thyme and Parmesan in a mixing bowl, gently tossing to coat.

Roll out the chilled dough into a 12-inch circle on a floured surface. Transfer to a lined baking sheet.

Spoon the roasted squash filling onto the center, leaving a 2-inch border. Fold edges over the filling and brush with egg wash or plant-based milk.

Bake at 375°F (190°C) for 30-35 minutes until golden brown. Watch edges to prevent over-browning.

Let cool for 10 minutes before slicing and serving warm.