Mix first 4 ingredients until smooth. In a large skillet, heat 2 tablespoons oil over medium-high heat; stir-fry chicken until no longer pink. Remove from pan. , In same pan, heat remaining oil over medium-high heat; stir-fry mushrooms, pepper, water chestnuts and ginger until pepper is crisp-tender, 3-5 minutes. Stir broth mixture and add to pan with green onions; bring to a boil. Cook and stir until sauce is thickened, 1-2 minutes., Stir in chicken and cashews; heat through. Serve with rice.