Dice onion and mix with pork, salt, pepper and sugar. Cut cabbage leaves in half and remove stems. Cut the scallions in half lengthwise. Boil a pot of water and give the cabbage and scallions a quick dip, remove and drain. Fill each cabbage leaf with pork filling, wrap and tie with a piece of scallion. Simmer cabbage rolls in broth for approx ½ hour before serving, add salt to taste.