Marinate Chicken: Add chicken pieces to a bowl with 2 Tablespoons soy sauce, 2 teaspoons oyster sauce, 1 1/2 teaspoons black pepper, and 1 teaspoon salt. Set aside. Add 1/2 cup cornstarch to a large bowl or resealable plastic bag and set aside.

Make Sauce: Mix sauce ingredients together and stir to combine.

Coat chicken in cornstarch: Remove chicken pieces from marinade and add to bowl or bag with cornstarch, tossing well to coat.

Sauté Chicken: Heat oil in a large skillet or wok over medium-high heat. Once hot, add 1/2 of the chicken pieces, spacing them out, so they can get golden and crisp on the outsides, flipping once, about 5 minutes, or until cooked through. Remove chicken to a plate, reserving the oil in the pan. Repeat with remaining chicken. Add more oil if needed.

Sauté Veggies: Pour a tiny bit more oil to the pan if needed and add onion, celery and bell pepper. Cook, tossing occasionally, over medium-high heat for a few minutes, until tender.

Finish: Add sauce and simmer until it begins to slightly thicken. Add chicken and stir to coat.

Serve over hot cooked rice.