Cut the chicken: Slice the boneless, skinless chicken into uniform 1-inch pieces. Prepare the marinade: In a bowl, combine the chicken pieces with the egg white, cornstarch, Shaoxing wine, light soy sauce, and salt. Mix well until every piece of chicken is coated. Marinate: Let the chicken marinate for at least 15 minutes at room temperature, or up to 30 minutes in the refrigerator. Velvet the chicken: Heat 2 tablespoons of vegetable oil in a wok or large skillet over medium-high heat. Add the marinated chicken in a single layer, ensuring not to overcrowd the pan. Stir-fry for 2-3 minutes until the chicken is mostly cooked through and opaque, but still very tender. Alternatively, you can blanch the chicken: bring a pot of water to a gentle simmer, carefully add the marinated chicken, and cook for 1-2 minutes until just cooked through. Remove with a slotted spoon. Drain and set aside: Remove the velveted chicken from the wok or water and drain any excess oil or water. Set aside to use in your Kung Pao or other stir-fry recipe. Prepare your Kung Pao sauce: While the chicken is velveting, prepare your Kung Pao sauce according to your chosen recipe, ready to combine with the tender chicken.