Prepare the Chicken: In a medium bowl, whisk together the egg white and 1 tablespoon of cornstarch until smooth. Add the sliced chicken, tossing to coat. Let it marinate for 10 minutes to tenderize the meat.
Cook the Chicken: In a large skillet or wok, heat ½ tablespoon of vegetable oil over medium-high heat. Add the chicken slices in a single layer and cook until lightly browned and just cooked through, about 3-4 minutes.
Stir-Fry the Aromatics and Vegetables: Add the remaining ½ tablespoon of oil to the skillet. Add garlic and ginger, stir-frying for about 30 seconds until fragrant. Add the mushrooms, snow peas, carrots, water chestnuts, and bamboo shoots, cooking until the vegetables are tender-crisp, about 3-4 minutes.
Make the Sauce: In a small bowl, whisk together the chicken stock, remaining 1 teaspoon of cornstarch, sugar, soy sauce, and sesame oil.
Combine and Cook: Return the chicken to the skillet with the vegetables. Pour in the sauce mixture, stirring continuously until the sauce thickens and coats the chicken and vegetables evenly, about 1-2 minutes.
Serve: Serve hot with steamed rice or noodles for a complete, satisfying meal.