In a large bowl, combine flour and salt. Create a well, add warm water gradually while stirring until shaggy clumps form.
Knead the dough in the bowl for 1 minute, cover with a damp towel and rest for 10 minutes. Knead on a floured surface for 3-4 minutes until smooth, then rest covered for 30 minutes.
Toss chopped napa cabbage with 1 teaspoon salt and let sit for 15-20 minutes. Squeeze firmly in a kitchen towel to remove excess moisture.
Combine ground pork, squeezed cabbage, scallions, ginger, garlic, soy sauce, sesame oil, Shaoxing wine, white pepper, and beaten egg. Mix in one direction for 3-4 minutes until sticky. Refrigerate until ready to use.
Roll the rested dough into a 1-inch thick rope and cut into 24-28 equal pieces. Flatten each piece into a disc.
Roll each disc from the edges toward the center, rotating after each roll, until you have a 3-3.5 inch circle with thinner edges and a slightly thicker center.
Place 1 tablespoon of filling in the center of a wrapper. Moisten the edges with water. Fold in half and pleat the edges to seal completely.
For boiled dumplings: Cook 8-10 dumplings in boiling water. Add 1/2 cup cold water when it returns to a boil, repeat twice. Drain when dumplings float and look translucent.
For potstickers: Pan-fry dumplings in 1 tablespoon oil over medium-high heat for 2-3 minutes until bottoms are golden. Add 1/4 cup water, cover and steam for 5-6 minutes. Uncover and cook 1-2 minutes to re-crisp.
Combine soy sauce, Chinese black vinegar, sesame oil, and minced garlic in a small bowl. Add chili oil if desired. Serve alongside hot dumplings.