Wash the bak choy and remove each leave until you have a small middle piece
Using a small knife, create a small slit in the stems so that the stems cook the same time as the leaves (if the stem is on the bigger side, create a slit shaped like a cross)
Run the chicken breast under cold water to remove any dirt during packaging (this will not get rid of salmonella, but because the meat could have been on the floor, better safe than sorry to wash it real quick)
Pat dry the meat and slice into thin pieces
Marinade the chicken with soy sauce, sugar, and corn starch and place in the fridgr for at least 30 minutes
Boil the bak choy in hot water until the stems are close to transparent (about 3 - 4 minutes)
Drain the bak choy
In the wok, heat up the oil in Medium High and add ginger (about a min)
Quickly add in the onion and cook for about 30 seconds
Add in the chicken and turn the heat down to Medium and spread evenly so that all chicken pieces cook, flipping regularly so the chicken cooks close to 90% done (add more oil if needed)
Add in the bak choy and mix well. Cover and cook for an additional 2 minutes
Add salt to taste