1. Combine the hoisin sauce, soy sauce, vinegar, honey, ginger, garlic, and sesame oil in a bowl large enough to hold the chicken. Transfer 1/4 cup of the mixture to a small bowl, and reserve for glazing. Add the chicken to the bowl, turning to coat. Cover and refrigerate for 1 hour.
2. Heat a gril or grill pan to medium-high. Grill the chicken 3 minutes per side, or until just cooked through. Brush with some of the reserved glaze, turn and cook 30 seconds left. Move to a platter; shower with the scallions and sesame seeds if you so chose.