Prepare the sauce first: In a small dish, mix equal parts cornstarch and water. Combine the cornstarch and water in a medium saucepan, then add the rest of the ingredients. Bring sauce to a simmer while stirring regularly. Let the sauce thicken a little bit. The sauce will be a deep chocolate color. Take the sauce off the fire as soon as it reaches the desired thickness and let it cool fully. (place in the fridge to hasten the process)

Place the chicken cubes in a big ziplock bag and pour half of the cooled sauce over them. Smother the chicken in the sauce and shake gently to coat. Allow the chicken to marinade in the refrigerator for at least 30 minutes. Save the leftover sauce for later use.

When you're ready to cook the chicken, remove it from the marinade, thread it onto skewers, and fire up the grill.

Insert skewers into hot, lightly greased barbecue grates. The chicken should be cooked thoroughly (an internal temperature of 165 degrees) after 20-30 minutes, turning every 3-4 minutes. In the last couple of turns, baste the chicken with the leftover teriyaki sauce.

When done, take skewers from the grill and serve with optional chopped green onion and toasted sesame seeds.