Chop cabbage, Chinese chives, and spring onion finely and set aside.
Remove the skin from the ginger and grate finely.
Using a garlic mincer, mince the garlic and set aside.
Mix the pork mince, shredded cabbage, spring onion, ginger, garlic, soy sauce, sake, sesame oil, salt and pepper together in a bowl.
Mix together well until they become well combined and sticky in texture.
Spoon about a tablespoon of the mixture into the centre of a Gyoza wrapper and fold while pinching the sides together to close the Gyoza. Use your thumbs to fold it and use your right index finger to push mince filling in (see photo or mini video if you are not familiar with this method) .
Heat a fry pan over medium heat and place the Gyoza in the pan and brown the bottom part of the Gyoza.
Once the Gyoza is slightly browned on the bottom, pour ¼ cup hot water into the pan to steam fry the Gyoza.
Put a lid on the pan to steam the Gyoza and turn the heat up to high. Steam cook for about 3 minutes.
Take the lid off and let the water evaporate. Carefully pour a little bit of sesame seed oil around the Gyoza to make the bottom turn crisp and golden brown.
Turn off the heat and serve the Gyoza on a plate with the bottom up for best presentation.
* I recommend to use Japanese gyoza wrapper. I found that Chinese wrapper is thicker than Japanese gyoza wrapper.