Squash Pot Stickers

Put squash, 2 tablespoons soy sauce, sugar, and salt in a medium saucepan. Cover with water; bring to a boil over medium-high heat. Cook until squash is very soft, about 12 minutes; drain. Transfer to a medium bowl; mash with a fork until smooth. Stir in scallions and ginger. Stir together sesame seeds, 1/4 cup water, and remaining 1/2 cup soy sauce in a bowl; set sauce aside.

Place 1 scant tablespoon filling in the center of each wrapper; brush edges with water. Bring up corners to make a triangle; press to seal. Place on a baking sheet; freeze until firm, 10 to 15 minutes.

Heat 2 tablespoons oil in a large nonstick skillet over medium heat until hot but not smoking. Add 10 potstickers, and cook, shaking pan frequently, until bottoms are golden brown. Turn pot stickers over; very carefully pour in 1/2 cup water, and cover. Steam until most liquid is evaporated, 2 to 3 minutes. Transfer to a serving dish; cover with foil to keep warm. Repeat with remaining oil and pot stickers. Serve with dipping sauce.