1Place the finely chopped napa cabbage in a clean kitchen towel and twist firmly to extract all excess moisture, until barely any liquid remains, about 2-3 minutes of squeezing.
2Combine the squeezed-dry cabbage with ground pork, minced garlic, ginger, scallions, soy sauce, sesame oil, sugar, white pepper, salt, and cold water in a large mixing bowl. Mix vigorously in one direction using chopsticks or a spoon until the mixture becomes slightly sticky and cohesive, about 2 minutes. Cover and refrigerate for 30 minutes to firm up the filling for easier handling.
3Prepare your wrapping station by placing gyoza wrappers on a clean surface and covering them with a lightly dampened kitchen towel to prevent drying. Fill a small bowl with water for sealing.
4Place one wrapper flat on your palm and spoon 1 tablespoon of filling into the center. Dip your finger in water and moisten the entire edge of the wrapper. Fold the wrapper in half to create a half-moon shape, then create 5-6 pleats along one side only, pressing firmly to seal completely with no air pockets. Stand the gyoza on its flat bottom to ensure it sits upright. Repeat with remaining wrappers and filling.
5Heat 1½ tablespoons vegetable oil in a large non-stick skillet over medium-high heat until shimmering, about 2 minutes. Arrange gyoza flat-side down in a circular pattern, working in batches of 10-12 to avoid overcrowding. Let them sear undisturbed until the bottoms turn golden-brown and crispy, about 3 minutes.
6Pour in ⅓ cup water carefully (it will splatter), immediately cover with a tight-fitting lid, and reduce heat to medium. Steam until the water evaporates completely and the wrappers become translucent, about 6-8 minutes. Remove lid and continue cooking for 30 seconds to re-crisp the bottoms.
7Transfer gyoza to a serving plate with the crispy side facing up. Repeat the pan-frying and steaming process with remaining gyoza, adding fresh oil between batches. Serve immediately with your favorite dipping sauce while hot and crispy.