To make the marinade: In a medium bowl, whisk together all ingredients except the short ribs. Place the short ribs in a rectangular baking dish and pour the marinade over them. Turn the ribs in the marinade to coat the meat evenly. Cover and refrigerate for at least 4 hours or overnight, turning the ribs in the marinade once or twice.
To grill: Prepare a hot fire in a charcoal or gas grill.
Lightly coat the green onions in the oil and season with salt.
When the grill is hot, lightly oil the grates.
Remove the short ribs from the marinade, letting excess drip off, and place them on the grill, along with the green onions, working in batches if needed.
Grill until they are nicely charred on both sides, about 2 minutes for the green onions and 5 to 8 minutes for the short ribs. Remove them from the grill as they are cooked.
Sprinkle the short ribs with sesame seeds and serve with rice.