Trim off the stem of the bok choy, separate the stalks, and rinse each clean of dirt and debris. Cut each stem into 2-inch pieces, then spit them in half or thirds lengthwise. Set aside. (If using baby bok choy, just trim the stems and rinse well.)
Set the cold wok on the burner, pour in 2 tablespoons of the canola oil down the side of the wok and swirl to distribute. Add the garlic and ginger and turn on the heat, cooking until the wok is hot. Keep an eye on it so the garlic and ginger don’t burn.
Add the sliced chicken and cook for about 2 minutes, until the meat starts turning white. Remove to a plate and cover.
Pour in the rest of the canola oil and the bok choy (can do it in two batches if necessary). Stir for about 2 minutes, then add the scallions and cook until the vegetables are bright green and just tender.
Return the chicken to the wok and add the soy sauce and chicken stock. Cook for form 1 to 2 minutes, until evenly heated.