In a large bowl, combine the ground pork, finely chopped cabbage, green onions, minced garlic, minced ginger, soy sauce, sesame oil, rice vinegar, sugar, salt, and pepper.
Mix well until all ingredients are thoroughly combined.
Place a gyoza wrapper on a clean surface.
Spoon about 1 teaspoon of the filling into the center of the wrapper.
Moisten the edges of the wrapper with a little water.
Fold the wrapper in half to create a half-moon shape, pressing the edges together to seal.
Pleat the sealed edge, pressing firmly to ensure the gyoza is well sealed.
Repeat with the remaining wrappers and filling.
Heat 1 tablespoon of vegetable oil in a large non-stick skillet over medium-high heat.
Arrange the gyoza in the skillet, flat side down, making sure they are not touching.
Cook for 2-3 minutes until the bottoms are golden brown.
Add 1/4 cup of water to the skillet and immediately cover with a lid.
Reduce the heat to medium and cook for about 5 minutes, or until the water has evaporated and the gyoza are cooked through.
Remove the lid and cook for an additional 1-2 minutes to re-crisp the bottoms.
In a small bowl, combine the soy sauce, rice vinegar, sesame oil, and chili oil (if using).
Enjoy your meal!