Make the dough: In a medium bowl, whisk together flour, sugar, and salt. Using a pastry blender or your fingers in a snapping motion, cut butter into flour mixture until you have mostly pea-sized pieces of butter. Add ice water and mix just until dough comes together. Press dough into a disk, wrap in plastic, and refrigerate for 45 minutes or up to 2 days.Make the filling: Preheat oven to 350 degrees. Slice butternut squash into ¼-inch wide slices, similar to melon slices. Toss squash slices with olive oil, salt, pepper, and thyme. Spread over sheet pan in a single layer and roast until squash is just starting to turn golden brown, about 20 minutes. This can be done a day ahead. Squash will be baked again in the assembled galette, so don’t roast too much at this point or it will be very chewy after the final bake.To assemble: While squash is baking, roll out cold dough on a floured surface to a 12-inch circle. Return to fridge to rest until squash has cooled to room temperature, or at least 20 minutes. Spread goat cheese on galette dough, leaving a 2-inch border. Layer and stack about 2 cups of squash over the goat cheese. (You may have some extra left for snacking.) Fold the dough border over the filling, folding dough onto itself every couple of inches. Chill assembled galette for 10 to 15 minutes. Brush crust with egg wash and sprinkle with extra thyme leaves. Bake until the crust is golden brown, about 40 to 45 minutes. Remove from oven and let cool for 10 minutes before serving.From No Pressure Pie.