Dissolve the cornstarch in the chicken broth, and stir in the soy sauce, ginger, and hot sauce; set aside. Heat half of the oil in a wok or large skillet over high heat. Stir in the chicken; cook and stir until the chicken is no longer pink, about 5 minutes. Remove the chicken from the wok, and set aside.
Pour the remaining tablespoon of oil into the wok, and stir in the onion, green bell pepper, and water chestnuts. Cook and stir until the chestnuts are hot, and the onion has softened, about 5 minutes more. Stir up the sauce to redistribute the cornstarch, then pour into the wok, and bring to a boil. Add the reserved chicken, and stir until the sauce thickens, and the chicken is hot. Sprinkle with cashews to serve.