Partially freeze meat. Thinly slice across the grain into bite-size strips.
Meanwhile, for sauce, stir together chicken broth, cornstarch, soy sauce, dry sherry, and red pepper. Set aside.
Spray a wok or large skillet with nonstick spray. Add onion, broccoli, garlic, and gingerroot and stir-fry for 3 minutes or till vegetables are crisp-tender. Remove vegetable mixture from wok.
Add oil to hot wok. Add pork and stir-fry for 2 to 3 minutes or till no longer pink. Push pork from center of wok.
Stir sauce and add to the center of wok. Cook and stir till thickened and bubbly.
Return vegetables to wok. Add water chestnuts and stir all ingredients together to coat with sauce. Cook and stir for 1 to 2 minutes more or till heated through.