Mix together ground beef, green onions, minced garlic, rice wine, soy sauce, sesame oil, cornstarch, sesame seeds, and sugar in a bowl.

Shape the meat mixture into 1-inch balls.

Place the meatballs on a large pan and refrigerate for at least an hour to retain shape.

Soak wooden skewers in warm water for 20-30 minutes to prevent burning.

Prepare a grill or heat a broiler.

Thread 2-3 meatballs per skewer.

Grill over medium coals for 5-6 minutes per side, or until the juices run clear.

Serve with sweet and sour sauce and hot table mustard, if desired.

To prepare a simple table dipping mustard, mix mustard powder with a small amount of water to make a pleasant consistency; allow to ripen for 5-10 minutes.