Preheat oven to 400 degrees F. Lightly coat a 2-quart rectangular baking dish with cooking spray; set aside.
For sauce, in a medium bowl combine broth, hoisin sauce, ginger, cornstarch, crushed red pepper, and black pepper; set aside.
Lightly coat an extra-large skillet with cooking spray; heat skillet over medium-high heat. Add chicken; cook until lightly browned, turning once. Remove from skillet. Add bok choy, onion wedges, celery, carrots, and sweet pepper to skillet. Cook for 3 to 4 minutes or until vegetables start to soften, stirring occasionally. Add garlic; cook and stir for 30 seconds more. Stir in sauce. Cook and stir about 3 minutes or until sauce is thickened and bubbly. Stir in chicken and cooked rice.
Transfer chicken mixture to the prepared baking dish. Bake, covered, about 20 minutes or until chicken is no longer pink (165 degrees F) and edges are bubbly. Sprinkle with chow mein noodles and cashews. Bake, uncovered, for 4 to 5 minutes more or until noodles and cashews are golden. Sprinkle with green onions.