In a medium bowl, whisk together ¼ cup brown sugar, ½ cup soy sauce, ¼ cup rice wine vinegar, ¼ cup honey, 2 tsp minced garlic, ½ tsp ground ginger and ½ tsp black pepper.

Reserve ½ cup of the marinade in a separate bowl for the finishing sauce.

Place 2 lbs boneless skinless chicken thighs into a gallon-size zip-top bag or shallow dish.

Pour the remaining marinade over the chicken, making sure all pieces are well coated.

Refrigerate and marinate for at least 30 minutes, or up to 8 hours.

Preheat the grill to medium-high heat (375–400°F).

Lightly oil or spray the grill grates to prevent sticking.

Remove the chicken from the marinade and discard the used marinade.

Grill the chicken for 5–7 minutes per side, or until the thickest part reaches an internal temperature of 165°F.

While the chicken cooks, whisk 1 Tbsp cornstarch into the reserved ½ cup marinade.

Pour the sauce into a small saucepan and cook over medium-high heat, whisking constantly for 2–3 minutes, until the sauce thickens.

Brush the thickened glaze over the grilled chicken just before serving.

Garnish with sliced green onions and sesame seeds, if desired.