If the spareribs are still attached to each other, cut between them to separate them (or you could ask your butcher to do this when you buy them). Place the spareribs in a large bowl.
Mix together all the remaining ingredients except the scallions; pour this mixture over the ribs. Toss well to coat evenly. Cover the bowl and let marinate in the refrigerator overnight.
Cook the ribs on a medium-hot grill, turning frequently, for 30 - 40 minutes. Brush occasionally with the remaining marinade.
While the ribs are cooking, finely slice the scallions. Sprinkle them over the ribs and serve immediately.