Heat the sesame seed oil over medium heat with the green onion and garlic and saute for about 3 minutes.
Add the orange juice and lemon zest and bring to a slow boil for about 2 minutes.
Add the soy sauce, the vinegar, 1/2 cup of chicken stock, ground ginger, chili sauce (optional), and the brown sugar and stir.
Separately, in a small bowl, stir together the remaining chicken stock with the corn starch and once combined, add to the sauce.
Mix everything well, and let it simmer until it has thickened.
Season with more salt or sugar depending on the taste.
Toss together with the chicken, add sesame seeds on top and enjoy!