To make the filling: Add the ground pork and salt to a bowl and mix until the pork starts to become sticky. Add the white pepper, soy sauce, oyster sauce, dark soy sauce, and sesame oil and mix well. Add the egg and chicken stock and continue mixing until fully incorporated. Add the ginger, scallions, and garlic chives and mix until evenly combined.
To fill the pastry bag: Place a pastry bag or zip-top bag inside a glass to hold it open. Transfer the pork filling to the bag, tie or close the opening, then cut off the tip.
To wrap the potstickers: Place the gyoza or dumpling wrappers on a flat surface. Pipe a line of filling across the center of each wrapper. Dab a little water on the wrapper if needed, then fold it in half and press firmly to hold it together. There’s no need to pleat or completely seal the entire edge.
To pan-fry the potstickers: Add the cooking oil to a pan and spread it evenly. Arrange the potstickers flat-side down while the pan is still off the heat. Turn the heat to medium and pan-fry for about 1 minute, until the bottoms begin to set.
To steam the potstickers: Carefully pour in the water and immediately cover with a lid. Steam for about 6 minutes, or until the pork is completely cooked through and reaches an internal temperature of at least 160°F (71°C).
To crisp the bottoms: Remove the lid and let the remaining water cook away. Once the water has evaporated, leave the potstickers undisturbed for about 1 minute, until the bottoms are golden and crispy.
To finish and serve: Sprinkle the scallion over the potstickers. Drizzle with soy sauce and chili oil, or serve them on the side for dipping. Serve immediately while hot and crispy.