Finely chop the Napa cabbage, sprinkle with salt, and let it sit for 10 minutes. Squeeze out ALL the water — this is critical. Watery cabbage = watery filling = soggy, falling-apart gyoza. I learned this the same way I learned it with pierogi filling: the hard way, approximately three times. Once the cabbage is dry, mix it with the pork, green onions, garlic, soy sauce, sesame oil, ginger, and white pepper. Stir in one direction until the filling is cohesive — this helps the protein bind and creates a better texture.