Rinse chicken and pat dry.  Cut into 1" cubes.  Set aside.  In a small bowl, combine broth, cornstarch, sherry, soy sauce and vinegar.  Set aside.

 

Heat hot pepper oil in a nonstick skillet or wok over high heat.  Add ginger and garlic and saute 1 minute.  Add chicken and stir-fry until lightly browned.  Transfer chicken to plate and set aside.  Add sesame oil to skillet.  Stir in mushrooms and pepper.  Cover pan, reduce heat to medium-high and steam 5 to 7 minutes.  Add chicken broth mixture.  Return chicken to pan and cook until sauce is thickened.  Add onions and cashews and cook 2 minutes more.  Serve over rice if desired.