1.  In a large skillet, brown chicken in oil. Cover and cook until juices run clear, about 20 minutes. Remove chicken; keep warm.

2.  In the same skillet, saute mushrooms and onions until tender. Stir in wine or broth, butter, salt, and pepper.

3.  In a small bowl, combine cornstarch and water until smooth; add to skillet. Bring to a boil; cook and stir for 2 minutes or until thickened. Return chicken to skillet; heat through.