01 - In a mixing bowl, whisk together the soy sauce, mirin, brown sugar, honey, rice vinegar, sesame oil, minced garlic, and grated ginger until the sugar dissolves and the mixture is well combined.
02 - Measure out and set aside 3 tablespoons of the marinade to use later as a finishing glaze.
03 - Place the cubed chicken in a large bowl or zip-top bag. Pour the remaining marinade over the chicken and toss to coat evenly. Refrigerate for at least 30 minutes, or up to 2 hours for deeper flavor penetration.
04 - If using wooden skewers, submerge them in water for at least 30 minutes to prevent burning during cooking.
05 - Remove the chicken from the marinade, letting excess drip off. Thread the cubes onto skewers, spacing them evenly for uniform cooking.
06 - Heat an outdoor grill or indoor broiler to medium-high, ensuring the grates or rack are clean and lightly oiled.
07 - Grill or broil the skewers for 12 to 15 minutes, turning occasionally, until the chicken is cooked through (internal temperature reaches 165°F) and lightly charred on the edges.
08 - While the skewers cook, pour the reserved marinade into a small saucepan and bring to a gentle simmer over medium heat for 2 to 3 minutes. For a thicker glaze, stir in the cornstarch mixed with a splash of water and cook until the sauce coats the back of a spoon.
09 - Brush the cooked skewers generously with the teriyaki glaze. Garnish with toasted sesame seeds and sliced spring onions. Serve immediately alongside steamed rice or grilled vegetables.