Prep the kimchi and cabbage: Finely chop the kimchi and squeeze out as much liquid as you can.
Toss chopped napa cabbage with a pinch of salt, let sit 10 minutes, then squeeze dry.
Make the filling: In a bowl, combine ground pork (or crumbled, pressed tofu), kimchi, cabbage, green onions, garlic, ginger, soy sauce, sesame oil, gochugaru, sugar, and a little pepper. Mix until sticky and cohesive. Adjust salt to taste.
Set up your station: Place a small bowl of water, the wrappers, and a tray lined with parchment nearby.
Fill and fold: Add about 1 tablespoon of filling to the center of a wrapper.
Dab water along the edge. Fold into a half-moon, pressing out air, and pleat the seam. For square wrappers, fold corner-to-corner into a triangle, then crimp the edges.
Keep completed dumplings covered with a towel.
Pan-fry (potsticker style): Heat 1–2 teaspoons oil in a nonstick skillet over medium-high. Add dumplings flat-side down and cook until bottoms are golden, 2–3 minutes. Carefully pour in 1/4 cup water, cover, and steam 4–5 minutes.
Uncover and cook 1 minute to re-crisp.
To steam: Place dumplings in a lined steamer basket over simmering water. Steam 8–10 minutes, until cooked through.
To boil: Drop into gently boiling water. Stir to prevent sticking.
When they float, cook 2–3 minutes more. Great for serving in broth.
Serve: Mix the dipping sauce ingredients and serve warm dumplings right away.