In a small bowl, whisk together the cornstarch with 2 tablespoons of the water until smooth. Set aside.

In a medium saucepan, combine the remaining water, brown sugar, soy sauce, garlic, rice vinegar, ginger, honey, and sesame oil. Add the cornstarch mixture and stir well.

Place the saucepan over medium heat and bring the mixture to a simmer, stirring frequently. Let it cook for 2–3 minutes until the sauce thickens and turns a deep brown color. Remove from heat and allow the sauce to cool completely. You can speed this up by placing it in the refrigerator.

Once the sauce is completely cool, place the cubed chicken in a large resealable plastic bag. Pour half of the sauce over the chicken, seal the bag, and gently shake to coat all pieces. Refrigerate for at least 30 minutes, or up to 4 hours for deeper flavor. Set the remaining sauce aside for basting.

When the chicken has marinated, thread the cubes onto the skewers, leaving a small gap between pieces. Preheat your grill to medium heat (about 350°F).

Lightly oil the grill grates, then place the skewers on the grill. Cook for 20–30 minutes, turning every 3–4 minutes, until the chicken is cooked through and reaches an internal temperature of 165°F. During the last few turns, brush the skewers with the reserved teriyaki sauce.

Remove the skewers from the grill and let them rest for a minute. Garnish with chopped green onions and a sprinkle of sesame seeds if desired. Serve over steamed rice.