01 - In a large bowl, whisk together flour and salt. Cut in the cold butter using a pastry blender or your fingers until the mixture resembles coarse crumbs. Gradually add ice water, mixing just until the dough comes together. Form into a disk, wrap in plastic, and chill for 30 minutes.
02 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
03 - Toss the butternut squash, apples, and red onion with olive oil, thyme, salt, and pepper. Spread on the prepared baking sheet and roast for 20–25 minutes, stirring once, until the squash is tender and golden. Cool slightly.
04 - On a lightly floured surface, roll out the pastry to a 12-inch circle. Transfer to a parchment-lined baking sheet.
05 - Arrange the roasted squash, apples, and onions in the center of the pastry, leaving a 2-inch border. Sprinkle with goat cheese and drizzle with honey if using.
06 - Fold the pastry edges over the filling, pleating as needed. Brush the crust with beaten egg and sprinkle with coarse sea salt if desired.
07 - Bake for 25–30 minutes, or until the crust is golden brown. Let cool for 10 minutes before slicing and serving.