In a large mixing bowl, combine all the gyoza filling ingredients: ground pork, chopped napa cabbage, minced garlic, grated ginger, chopped green onions, soy sauce, sesame oil, salt, and black pepper. Mix well until the filling is thoroughly combined.
To assemble the gyoza, place a gyoza wrapper in your palm. Add about a teaspoon of the filling in the center of the wrapper.
Moisten the edge of the wrapper with water using your fingertip. Fold the wrapper in half, creating a half-moon shape, and press the edges firmly to seal. You can also create pleats along the sealed edge for a decorative touch.
Repeat the process with the remaining wrappers and filling.
Heat 2 tablespoons of vegetable oil in a large skillet over medium-high heat. Place the gyoza in the skillet, flat side down, and cook until the bottoms turn golden brown (about 2-3 minutes).
Pour in 1/2 cup of water and immediately cover the skillet with a lid. Steam the gyoza for 4-5 minutes or until the water has evaporated.
Remove the lid and continue cooking for an additional 2-3 minutes, allowing the bottoms to crisp up again.
While the gyoza cook, prepare the dipping sauce by mixing soy sauce, rice vinegar, sesame oil, and chili oil (if using) in a small bowl.
Serve the hot gyoza with the dipping sauce. Enjoy your homemade gyoza!
