First, slice your chicken into 1 ½ to 2 inch pieces, about ¼ inch thick. Remember to slice across the grain, especially if using chicken breast.
Add the water and soy sauce (or oyster sauce) to the chicken in a medium bowl, and mix until the chicken is well-coated. Set aside for 5-10 minutes. In that time, most of the liquid will be absorbed into the chicken.
Add the cornstarch and vegetable oil and mix again until everything’s incorporated and the chicken is uniformly coated. For the best results, let the chicken sit for 15 to 20 minutes to marinate.
To sear, place your wok over high heat. When it starts to smoke lightly, add a couple tablespoons of vegetable oil to coat the surface of the wok. Add the chicken in one layer, and allow to sear for 20 seconds. Stir-fry until the chicken has turned opaque, and remove from the wok.
To blanch, add the chicken to a wok filled with boiling water. When it turns opaque, cook for an additional 10 seconds (the chicken will be cooked 80% through). Then, remove from the wok.
Remember, in both scenarios, you will be cooking the chicken again in your stir-fry, so avoid overcooking it during the pre-cook process!
Note: We provided measurements for velveting 12 ounces (340g) of chicken, which is typical for one stir-fry dish. Adjust the amounts proportionally if you are making more or less.