1Place hens in resealable freezer plastic bag or large shallow glass dish. In small bowl, mix soy sauce, brown sugar, sesame oil, gingerroot, pepper flakes, 3 tablespoons onions and the garlic; pour marinade over hens. Seal bag or cover dish. Refrigerate at least 8 hours but no longer than 24 hours.
2Heat gas or charcoal grill. Remove hens from marinade; discard marinade. Place hens, cut sides down, on grill over high heat. Cover grill; cook 14 to 16 minutes, turning occasionally, until juice of hens is clear when thickest pieces are cut to bone (at least 165°F). Let stand 5 minutes before serving. Sprinkle with sesame seed and green onions.