FOR THE DUMPLINGS:
1 head napa cabbage
1 lb. ground pork
1/2 bunch Chinese chives or scallions, trimmed and minced
2" piece ginger, peeled and finely chopped
2 tbsp. soy sauce
2 tsp. sesame oil
1/2 tsp. salt
4 tbsp. vegetable oil
5 1/2 cups flour
FOR THE DIPPING SAUCE:
3 tbsp. soy sauce
3 tbsp. white vinegar
1. For the dumplings: To make filling, put cabbage into a large pot, cover with water, cover pot with lid, and bring to a boil over high heat. Reduce heat to medium and simmer until soft, 15–20 minutes. Drain; set aside to cool, then squeeze out excess water. Finely chop cabbage and transfer to a large bowl. Add pork, chives, ginger, soy sauce, sesame oil, salt, and 1 tbsp. of the vegetable oil and mix well with your hands. Cover with plastic and refrigerate for at least 1 hour or overnight.
2. To make wrappers, put flour into a large bowl and gradually add 1I cups water, stirring constantly with 2 chopsticks or a fork until dough holds together. Turn out onto a lightly floured surface and knead until silky and smooth. Transfer to a clean bowl, cover with plastic, and refrigerate for at least 30 minutes or up to 3 hours. Divide dough into 8 pieces. With a rolling pin, roll out on a clean work surface into 1"-thick ropes, cut ropes into 1" pieces, then shape pieces into balls. Roll out balls into 3H" circles. Keep dough and skins covered with plastic wrap while you work to prevent them from drying out.
3. Working with 1 wrapper at a time, put 2 tsp. of the filling into center and fold dough over to form a half circle. Working from right to left, pleat edges together, turning dumpling halfway through to finish pleating remaining edges together. Transfer to a floured baking sheet; cover with plastic wrap. Repeat process with remaining wrappers and filling.
4. For boiled dumplings, bring a stockpot two-thirds full of water to a boil over high heat. Add uncooked dumplings and stir once to prevent them from sticking. Let water return to a boil, add 1 cup cold water, and return to a boil again. Repeat process 3 times, adding 4 cups cold water in all. Using a slotted spoon, transfer dumplings, draining briefly, to a serving platter. For panfried dumplings, heat the remaining 3 tbsp. vegetable oil in a large nonstick skillet over medium-high heat. Working in batches, add uncooked dumplings and H cup water, cover, and cook until bottoms begin to brown, about 10 minutes. Reduce heat to medium-low and continue cooking, covered, until filling is cooked through 8-10 minutes.
5. For the dipping sauce: Combine soy sauce and vinegar in a small dish and serve with boiled and panfried dumplings.
MAKES ABOUT 4 DOZEN