01 - Whisk together soy sauce, mirin, brown sugar, honey, rice vinegar, sesame oil, garlic, and ginger in a bowl until well combined.
02 - Set aside 3 tablespoons of the marinade in a separate small container for glazing later.
03 - Place chicken cubes in a large bowl or zip-top bag. Pour remaining marinade over chicken and toss to coat evenly. Refrigerate for at least 30 minutes, up to 2 hours for deeper flavor.
04 - If using wooden skewers, soak in water for 30 minutes before threading to prevent burning during cooking.
05 - Thread marinated chicken pieces onto skewers, leaving small space between pieces for even cooking.
06 - Heat grill or broiler to medium-high temperature.
07 - Grill or broil skewers for 12 to 15 minutes, turning occasionally, until chicken is cooked through and lightly charred on edges.
08 - While skewers cook, pour reserved marinade into small saucepan. Simmer over medium heat for 2 to 3 minutes. For thicker consistency, whisk cornstarch with splash of water and stir into sauce until thickened.
09 - Brush cooked skewers generously with teriyaki glaze. Sprinkle with toasted sesame seeds and sliced spring onions. Serve immediately with steamed rice or grilled vegetables.