01 - Whisk together soy sauce, mirin, brown sugar, honey, rice vinegar, sesame oil, minced garlic, and grated ginger in a mixing bowl until sugar is fully dissolved.
02 - Set aside 3 tablespoons of marinade in a separate bowl for glazing during cooking.
03 - Transfer chicken cubes to a large mixing bowl or resealable bag. Pour remaining marinade over chicken, tossing to coat evenly. Refrigerate for at least 30 minutes or up to 2 hours for deeper flavor.
04 - If using wooden skewers, soak them in water for 30 minutes to prevent charring during cooking.
05 - Thread marinated chicken cubes onto skewers, spacing pieces evenly.
06 - Heat grill or broiler to medium-high.
07 - Grill or broil skewers for 12 to 15 minutes, turning often, until chicken is cooked through and lightly charred.
08 - Meanwhile, pour reserved marinade into a small saucepan and bring to a simmer over medium heat. For a thicker glaze, stir in cornstarch mixed with a small amount of water and cook until thickened, about 2–3 minutes.
09 - Brush cooked chicken skewers generously with prepared teriyaki glaze.
10 - Sprinkle with toasted sesame seeds and sliced spring onions. Serve hot with steamed rice or grilled vegetables if desired.