1 lb. ground pork
1 large egg, lightly beaten
1 C. sliced scallions
1/4 C. Shaoxing rice wine or dry sherry
1/4 C. reduced-sodium soy sauce
2 T. mushroom dark soy sauce
2 T. minced fresh ginger
1 T. sesame oil
1 T. sugar
1 T. cornstarch, plus more for dusting
1 tsp. ground white pepper
1/4 tsp. salt
2 C. finely chopped Napa cabbage
80 round dumpling wrappers
7 T. canola oil, divided
3 1/2 C. warm water, divided
Combine pork, egg, scallions, rice wine, reduced-sodium soy sauce, mushroom dark soy sauce, ginger, sesame oil, sugar, cornstarch, white pepper and salt in a large bowl until well blended. Fold in cabbage.
Cover and refrigerate for at least 1 hour or overnight.
Set out dumpling wrappers and a small bowl of water; line three large baking sheets with parchment paper and dust with cornstarch. Place six wrappers on a clean work surface and spoon about 2 tsp. filling into the center of each.
Wet your finger and run it around the edge of a wrapper. Fold the wrapper over to form a half-moon shape and press the edges together to seal. Pleat the edges if desired.
Arrange the dumplings on a prepared baking sheet without letting them touch.
Heat 1 T. canola oil in a large nonstick skillet over medium-high heat. Add 12 dumplings (fresh or frozen) in a single layer not touching. Add 1/2 C. warm water to the pan. Cover and cook until starting to brown on the bottom, 6 to 8 minutes. Uncover and cook until all of the liquid is evaporated, about 30 seconds more. Repeat with the remaining oil, water and dumplings.
To make ahead: Freeze uncooked dumplings, uncovered, on the parchment-lined baking sheet until solid, at least 8 hours. Once frozen, transfer to an airtight container and freeze for up to 3 months.