Using your hands gently squeeze out as much excess water from the chicken pieces as possible, then dry using a paper towel/s.
For glaze; in a bowl whisk the soy sauce with cornstarch, ginger and sesame oil (if using) until smooth. then add in honey, brown sugar, ketchup and chili sauce; whisk/mix until combined (taste the sauce if you prefer a slightly sweeter taste then add in more honey or brown sugar).
In a small saucepan heat oil over medium-high heat.
Add in onion and saute for about 3 minutes or until slightly softened, then add in the chopped garlic and chili flakes and cook for about 2 minutes.
Add in the soy sauce mixture; bring to a simmer mixing constantly, cook until bubbly and thickened (the mixture will be fairly thick) set aside.
Heat a small amount oil in a skillet over medium-high heat (you may lightly season the chicken with black pepper before browning if desired but do NOT salt).
Add in chicken and brown on both sides; remove to prepared baking dish.
Pour the sauce over the chicken then using your hands or tongs turn the chicken pieces to coat in the sauce (make certain that the chicken is facing skin side up).
Bake uncovered for about 45 minutes or until completely cooked, basting with the pan glaze about halfway through cooking time.