1Sprinkle brown sugar over beef and mix well to evenly coat. Let sit at room temperature for 10 minutes while preparing marinade.
2In a bowl, whisk together remaining ingredients. Transfer beef into a large sealable freezer bag. Add marinade, press out excess air, and seal.
3Turn bag over several times to ensure beef is evenly coated. Refrigerate for at least 4 hours, preferably overnight.
4Heat gas or charcoal grill to medium-hot. Drain excess marinade off beef.
5Grill short ribs, turning once, to desired doneness, about 3–4 minutes per side.
6Garnish with thinly sliced green onions if desired. Serve whole or cut into smaller pieces with kitchen shears.
Notes
Korean-style short ribs (also known as 'flanken') are cut lengthwise across the rib bones, resulting in a thin strip about 8–10 inches long with 1/2-inch thick rib bones. Found at most Asian markets.