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 — this will be used later for the finishing glaze.
03 - Place the cubed chicken in a large bowl or zip-top bag and pour the remaining marinade over the pieces. Toss to coat evenly, then 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 30 minutes to prevent burning during cooking. Thread the marinated chicken pieces onto the skewers, distributing them evenly.
05 - Preheat a grill or broiler to medium-high heat. Cook the skewers for 12 to 15 minutes, turning occasionally, until the chicken is cooked through and lightly charred on the edges.
06 - While the skewers cook, pour the reserved marinade into a small saucepan and bring to a 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.
07 - 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.