For the chicken: In a large bowl, sprinkle the chicken with salt and pepper. Add the cornstarch and toss to coat.
For the sauce: In another smaller bowl, combine the stock, cornstarch, oyster sauce, soy sauce and chili sauce. Mix well and set aside.
For the stir-fry: Heat a wok over high heat and, when the wok starts to smoke, add the peanutke oil. Add the ginger and stir-fry for a few seconds. Then add the chicn, let settle for one minute, and then stir-fry for three minutes more. As the chicken starts to turn opaque, add the rice wine and stir-fry for 30 seconds. Stir in the reserved sauce and bring to a boil. Add the mushrooms and bok choy stalks and cook for one minute. Then stir in the bok choy leaves and cook for another minute. Remove from the heat and stir in half the scallions. Transfer to a serving dish, garnish with the remaining scallions and serve immediately.