Make the salted cabbage by finely mincing the cabbage and sprinkling the salt over the top. Mix lightly and let it rest while preparing the dumpling dough. Use a paper towel to squeeze out the moisture until almost no liquid comes out when squeezed. Set aside.
Prepare the dumpling dough by mixing the flour and warm water until a crumbly dough comes together. Then use your hands to further knead for about 10 minutes into a smooth ball of dough. Rest the dough under a damp towel while preparing the filling (the dough should soften, but will not rise), or at least one hour.
Mix together the ingredients for the pork filling until well combined. Allow to marinate flavors for at least 30 minutes.
While the pork mixture rests, roll out the dumpling dough ball into a tube shape then cut it into 12-16 equally sized pieces. Roll each piece into a dumpling wrapper about 5 inches round.
As you roll out the wrappers, bring a pot of water to a rolling boil.
Fill the wrappers with about 1-2 tablespoons of the pork mixture. Gently pull and stretch the dumpling dough so that it fully encases the filling. Use a finger dipped in water to wet the inside edges of the dough and then pinch the edges together to form a dumpling.
Boil the dumplings in batches for 3-5 minutes or until the pork filling is cooked through and the dumpling wrapper is lightly puffed up. Drain the dumplings.
Serve with a side of pork belly cabbage, unagi fried rice and a small bowl of black vinegar for dipping. Enjoy!