Whisk the broth with the cornstarch until smooth. Stir in the oyster sauce, soy sauce, vinegar, garlic, ginger, sugar and sesame oil. Set aside. Cut the chicken into bite size pieces; season with salt. Heat 1 tbsp oil in a wok or large skillet set over high heat. Add chicken; stir-fry for 5 minutes or until lightly browned. Transfer to a plate. Heat the remaining oil in the same wok. Add the onion, broccoli and red pepper; stir-fry for 5 minutes. Add reserved sauce; bring to a boil. Stir in the chicken. Cook, stirring for 3 minutes or until the chicken is cooked through and the vegetables are tender-crisp. Garnish with cashews and cilantro. Serve immediately.
Serve with whole grain rice or fragrant jasmine rice. Add 1 tbsp red Thai curry paste to the stir fry sauce for a spicy twist. Replace the oyster sauce with hoisin, if preferred.