Panda Express Black Pepper Chicken (Copycat)

chicken breast

stalks celery thinly sliced on a bias

medium white onion (, chopped into 3/4 - 1 inch squares (look at the photo for reference))

light soy sauce

ginger powder

chili vinegar*

coarse ground black pepper ((grind fresh, you want the punch of the large, coarse black pepper here. If you use plain black pepper it will completely overpower the dish and ruin it.))

corn starch

canola oil (, divided)