1 pound boneless, skinless chicken breasts, cut crosswise into 1/4-inch-thick bite-size slices
1 egg white, lightly beaten
1 tablespoon plus 1/2 teaspoon cornstarch, divided
2 teaspoons plus 2 tablespoons Shao Hsing rice wine (see Note) or dry sherry, divided
1/2 teaspoon salt, divided
3 tablespoons peanut oil or canola oil, divided
1/3 cup reduced-sodium chicken broth
2 teaspoons reduced-sodium soy sauce
1/4 teaspoon ground white pepper
6 cups water
2/3 cup chopped scallions, divided
1 tablespoon finely julienned or minced fresh ginger (see Tip)
1/4 teaspoon crushed red pepper
8 cups trimmed and halved baby bok choy (about 12 ounces)
1. Combine chicken, egg white, 1 tablespoon cornstarch, 2 teaspoons rice wine (or sherry) and 1/4 teaspoon salt in a medium bowl. Stir until the cornstarch is totally dissolved and no clumps are visible. Add 1 tablespoon oil and stir to combine. Marinate in the refrigerator, uncovered, for 30 minutes.
2. Meanwhile, combine broth, soy sauce, white pepper and the remaining 1/2 teaspoon cornstarch and 2 tablespoons rice wine in a small bowl.
3. When the chicken has 10 minutes to go, bring water to a boil in a large saucepan. Add 1 tablespoon oil. Reduce the heat to low. Carefully add the chicken to the barely simmering water; gently stir so it doesnt clump together. Cook just until opaque but not cooked through, about 1 minute. Carefully drain the chicken in a colander and shake to remove excess water.
4. Heat a 14-inch flat-bottomed wok over high heat until a bead of water vaporizes within 1 to 2 seconds of contact. Swirl in the remaining 1 tablespoon oil. Add 1/3 cup scallions, ginger and crushed red pepper; using a metal spatula, stir-fry until fragrant, about 10 seconds. Add bok choy and the remaining 1/4 teaspoon salt. Stir-fry until the bok choy is almost crisp-tender, 1 to 2 minutes. Add the chicken. Stir the broth mixture again, swirl it into the wok and stir-fry until the chicken is just cooked through and lightly coated with sauce, 30 seconds to 1 minute. Serve sprinkled with the remaining 1/3 cup scallions.