Combine first 6 ingredients in a medium bowl, stirring well; set aside. Cut chicken into 2-inch strips; add chicken to marinade, toss to coat.
Refrigerate in tightly covered container 8-24 hours.
Pour oil around top of a preheated wok or skillet, coating sides; heat on medium-high for 1 minute. Remove chicken from marinade. Place marinade in a small saucepan; bring to a boil, and cook 5 minutes. Set aside.
Add chicken to wok; stir fry 2-3 minutes. Remove chicken, and set aside. Add broccoli to wok, and stir fry 2 minutes. Add mushrooms; stir-fry 2 minutes or until crisp-tender. return chicken to wok; add marinade, stirring well. Combine cornstarch and water; add to wok. Cook stirring constantly, until thickened. Serve chicken mixture over fried Chinese noodles or hot rice.