2 cups all-purpose (plain) flour plus extra
cup boiling water
2 cups finely-chopped napa cabbage
cup chopped blanched spinach
1 pound ground (minced) dark chicken meat
teaspoon grated peeled fresh ginger
2 tablespoons finely-chopped garlic chives
1 teaspoon salt
teaspoon freshly-ground white pepper
1 tablespoon light soy sauce
1 teaspoon Asian sesame oil
teaspoon cornstarch (cornflour)
6 tablespoons distilled white vinegar
3 tablespoons light soy sauce
Chili oil as needed
To make the wrappers, in a food processor fitted with the metal blade, combine the 2 cups flour and salt and pulse once to mix. With the motor running, slowly pour in the boiling water. Continue to process until a rough ball forms and the dough pulls away from the sides of the work bowl, 15 to 20 seconds. Transfer to a lightly floured work surface. Knead until smooth and no longer sticky, about 2 minutes. Cover with a kitchen towel and let rest for 30 minutes.
To make the potstickers, put 1 tablespoon of the filling in the middle of a dough round. Fold the round in half and pinch the edges together at one end of the arc. Starting from that point, make 6 pleats or tucks along the curved edge to enclose the filling. As each potsticker is made, place seam-side up on a baking sheet, pressing down gently so it will sit flat. Cover with the kitchen towel and continue forming and placing the potstickers on the baking sheet until all are made.
Heat a 9-inch nonstick frying pan over medium-high heat. When hot, add about 2 teaspoons vegetable oil. Arrange 8 to 10 potstickers, seam-side up and just touching, in a spiral in the pan. Fry until the bottoms are browned, about 1 minute. Add water to come halfway up the sides of the potstickers and bring to a boil. Immediately cover, reduce the heat to low and steam-cook for 8 minutes, adding more water if necessary to keep the pan wet.
Divide the dipping sauce among individual saucers. Serve the potstickers hot with the sauce.