Make the filling: In a large bowl, combine ground pork, cabbage, garlic, ginger, scallions, chives, soy sauce, sake, mirin, sesame oil, white pepper, and salt. Mix well until evenly combined and slightly sticky.
Set up for wrapping: Place a small bowl of water next to your wrappers and keep wrappers covered with a damp towel so they don’t dry out.
Fill: Place 1 gyoza wrapper in your palm and add about 1 tablespoon filling to the center (don’t overfill).
Seal and pleat: Wet the edge of the wrapper with water. Fold in half. Create 5–6 pleats along the top edge, pressing firmly to seal. Set finished gyoza on a tray and keep covered.
Pan-fry: Heat a large non-stick skillet over medium-high. Add about 1 tablespoon oil and arrange gyoza flat-side down in a single layer. Cook 2–3 minutes until bottoms are golden and crisp.
Steam: Carefully add about 1/3 cup water and immediately cover with a lid. Steam 6–7 minutes, until water evaporates and filling is cooked through.
Crisp and serve: Remove the lid and cook 1–2 minutes more to re-crisp the bottoms. Serve hot with dipping sauce (soy sauce + rice vinegar; add chili oil and/or a drop of sesame oil if you like).