In a mixing bowl, combine sliced chicken breast with soy sauce, oyster sauce, and cornstarch. Stir until the chicken is evenly coated, then let it marinate for at least 15 minutes.

Place a wok or large skillet over high heat and add a couple of tablespoons of oil. Heat until it shimmers.

Carefully add the marinated chicken to the hot oil. Cook for about 3-5 minutes, stirring occasionally until the chicken is no longer pink.

In the same pan, toss in sliced carrots, mushrooms, snow peas, and water chestnuts. Stir-fry for about 2-3 minutes until tender-crisp.

Return the cooked chicken to the pan, add chopped green onions, and drizzle in additional soy and oyster sauce if desired.

Prepare a cornstarch slurry by mixing a tablespoon of cornstarch with a little water. Pour into the pan and stir until thickened.

Remove the pan from heat and serve hot over steamed or fried rice.