Whisk peanut oil, sherry, soy sauce, egg white, cornstarch, and red pepper flakes together in a large bowl. Add chicken, toss to coat, and marinate for 30 minutes. Remove chicken from marinade, shake to remove excess, and discard marinade.
Cook and stir garlic in a large skillet or wok until fragrant, about 1 minute. Stir marinated chicken pieces into skillet; cook and stir until cooked through, about 5 minutes.
Stir chicken broth, baby corn, snow peas, peanuts, green onions, and sesame oil into chicken mixture and cook until heated through, about 10 minutes.