In a bowl, mix together the chicken pieces and marinade ingredients. Let it marinate for at least an hour in the fridge.
In a small bowl, mix together all the ingredients for the sauce
Heat up a wok or large skillet on high heat with vegetable oil.
Once hot, add in marinated chicken pieces and cook until lightly browned on all sides.
Remove from pan and set aside.
Add more oil in your pan then turn heat down slightly before adding in garlic, peanut, celery, green bell pepper, and red bell pepper. Cook for a minute.
Add in the chicken pieces back into the pan and also add in the green onion then stir-fry quickly for about a minute.
Pour in the sauce mixture into the pan, stirring constantly. Cook until it starts to thicken slightly.
Serve hot over rice or noodles and enjoy your homemade Kung Pao chicken!