Marinate the Chicken: In a bowl, mix soy sauce, rice vinegar, and cornstarch. Add the chopped chicken pieces to the marinade and set aside for 10–15 minutes.
Prepare the Sauce: In a small bowl, whisk together chicken stock, soy sauce, rice vinegar, oyster sauce, and sesame oil. Set aside.
Stir-Fry the Chicken: Heat the peanut or vegetable oil in a large skillet or wok over medium-high heat. Add the marinated chicken and stir-fry for 2–3 minutes until lightly browned. Remove from the pan and set aside.
Cook the Vegetables: In the same pan, add garlic and cook until fragrant (about 30 seconds). Add the mushrooms, snow peas, bamboo shoots, and water chestnuts. Stir-fry for 2–3 minutes until the vegetables are crisp-tender.
Combine Chicken and Sauce: Return the chicken to the pan. Pour the prepared sauce over the chicken and vegetables, stirring well to coat everything evenly. Add the cornstarch-water mixture and stir until the sauce thickens (about 1 minute).
Season and Serve: Sprinkle with ground white pepper to taste. Serve immediately with steamed rice or noodles for a complete meal.