Tear off 4 (18- x 12-inch) heavy-duty aluminum foil sheets.
Place first 3 ingredients evenly in the center of each sheet; top each with 2 chicken thighs. Sprinkle with green onions.
Stir together 2 teaspoons sesame seeds and next 4 ingredients; spoon evenly over chicken.
Bring up 2 sides of each foil sheet, and double fold with about 1-inch-wide folds. Double fold each end to form a packet, leaving room for heat circulation inside packet.
Grill, covered with grill lid, over medium-high heat (350° to 400°) about 35 minutes or until chicken is done. Sprinkle with remaining 1 teaspoon sesame seeds before serving.
Prep: 10 min., Grill: 35 min.
Note: Hoisin sauce may be found in the Asian section of your grocery or in an Asian market.