Butterfly chicken breast in half. Remove all fat. Gently pound chicken with fingers to flatten. Coat with flour.
In large pan/skillet, heat oil on low. Brown chicken on each side. Remove chicken from pan.
Add butter to pan to melt. Add mushrooms and saute for a couple of minutes. Add chicken broth, wine and parsley. Bring to simmer. Add either more wine or butter to taste. Add chicken to heat through.