Whisk together egg white, vinegar, cornstarch, and salt in a large bowl until smooth. Add sliced chicken; mix to coat thoroughly. Cover with plastic wrap and marinate in the refrigerator for 30 minutes.

Bring water and oil to a boil in a pot over high heat. Reduce heat to medium.

Remove chicken from the marinade and shake off excess; discard remaining marinade. Add chicken to boiling water and cook until just white on the outside but not completely cooked through, about 1 minute.

Drain chicken and finish cooking in a hot oiled wok or skillet until no longer pink in the center and the juices run clear, or store parboiled chicken in the refrigerator in a sealed container until ready to use, up to a few hours.