01 - In a large bowl, whisk together flour and salt. Add cold cubed butter and cut in using a pastry blender or fingers until the mixture resembles coarse crumbs. Gradually add ice water, one tablespoon at a time, mixing just until dough forms. Shape into a disc, wrap in plastic, and refrigerate for at least 30 minutes.
02 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
03 - In a large bowl, toss diced butternut squash and sliced red onion with olive oil, thyme, nutmeg, salt, and pepper. Spread evenly on the prepared baking sheet and roast for 20 minutes.
04 - Remove baking sheet from oven, add apple slices, toss gently, and roast an additional 15 minutes until squash is tender and apples are slightly softened. Allow to cool briefly.
05 - On a lightly floured surface, roll the chilled dough into a 12-inch circle. Transfer carefully to a parchment-lined baking sheet.
06 - Spread the roasted squash, onion, and apple mixture evenly over the dough, leaving a 2-inch border. Sprinkle with crumbled goat cheese and chopped parsley if using.
07 - Fold the edges of the dough up and over the filling, pleating as necessary. Brush the crust with the beaten egg and sprinkle with coarse sea salt if desired.
08 - Bake in the preheated oven for 30 to 35 minutes, or until the crust is golden brown. Let cool slightly before slicing and serving.