Squash Manti With Gochujang Onions

Name: Squash Manti With Gochujang Onions
Ingredients: For the filling; 1/2 large yellow onion, fine-diced; 4 cups winter squash or pumpkin (approximately 1 large or 2 small kabocha, preferred for its sweetness), peeled and cut into 1-inch cubes; 2 cups Russet potatoes (approximately 1 large or 2 small potatoes), peeled cut into 1-inch cubes; 1 pound vegan ground beef (I like Meatless Farm Co. or Impossible), defrosted but not cooked; or extra-firm tofu, pressed and crumbled; 2 tablespoons kosher salt; 1/2 teaspoon freshly ground black pepper; 1/4 cup toasted sesame oil; 1 teaspoon ground coriander; 1 teaspoon Uzbek or Afghan wild cumin seeds, or ground cumin; 2 garlic cloves, minced; For the dough & topping; 1 large egg; 2 teaspoons kosher salt, divided; 1 tablespoon melted butter or vegetable oil; 6 cups all-purpose flour; 1/2 large yellow onion, thinly sliced; 1 tablespoon toasted sesame oil; 2 teaspoons gochujang; 2 scallions, green and white parts sliced thinly; 3 tablespoons toasted sesame seeds; 1 cup full-fat Greek yogurt or sour cream