Cut the cabbages in half lengthwise and trim the ends. Rinse and cut into pieces about 2 inch square. Place the cabbage into large resealable bags and sprinkle salt on the leaves so they are evenly coated. Use your hands to rub the salt in to the leaves. Seal the bags and leave at room temperature for 6 hours.
Rinse the salt from the cabbage leaves and then drain and squeeze out any excess liquid. Place the cabbage in a large container with a tight fitting lid. Stir in the fish sauce, green onions, white onion, garlic, sugar and ginger. Sprinkle the Korean chile powder over the mixture. Wear plastic gloves to protect your hands and rub the chile powder into the cabbage leaves until evenly coated. Seal the container and set in a cool dry place. Leave undisturbed for 4 days. Refrigerate before serving, and store in the refrigerator for up to 1 month (if it lasts that long!).
