Pour the mixture over the chicken, turn the pieces to coat evenly, cover and place in refrigerator a minimum of 3 hours, but preferably overnight.
Preheat grill or grill pan set to medium-low heat and oil the grates so it doesn't stick.
Grill chicken top side down first until well browned charred, about 2 to 3 minutes, turn and cook on the second side about 2 to 3 more minutes, careful not to burn.
Transfer to a serving platter and garnish with sesame seeds and scallions.