Finely chop the wombok and sprinkle 1/2 tsp of salt over it and leave it for about 5 minutes.
Squeeze out the excess water from the wombok and put the wombok in a bowl.
Add the pork mince, spring onion, soy sauce, sake, sesame oil, ginger juice, and remaining 1/2 teaspoon salt and pepper together in the bowl and mix.
Spoon about a tablespoon amount of the mixture into the centre of a gyoza wrapper and fold it while pinching the sides together to close the gyoza. Repeat this step till all the filling is gone.
Heat some oil in a fry pan over medium heat and place the gyoza in the pan and let it cook.
Pour half a cup of water into the pan and put a lid on it to steam the gyoza for about 5 minutes.
Take the lid off and let the water evaporate
Turn off the heat and serve the gyoza on a plate with the bottom up.