Stir the sugar into the soy sauce in a bowl until the sugar dissolves completely. Whisk the sesame oil, garlic, spring onions and sesame seeds into the soy sauce. Place the short ribs in a large, sealable bag and pour the marinade over the meat. Marinate in refrigerator for 8 hours or overnight.
Preheat an outdoor barbecue for medium heat, and lightly oil the grate. Remove the ribs from the bag; discard the marinade.
Cook the short ribs on the preheated barbecue until they are very firm, hot and grey in the centre, about 15 minutes per side. An instant-read thermometer inserted into the centre should read 70 degrees C.
Beef short ribs
You may need to special order these at your local butcher. If unavailable, substitute in pork spare ribs.