1. Cut chicken breasts in half. Place between sheets of waxed paper and pound slightly with mallet or large jar.
2. Heat oil in frying pan.
3. Sprinkle chicken with salt and pepper. Cook over high heat for five minutes on each side. Transfer to platter.
4. Add onion, lemon juice and parsley to pan. Cook one minute, stirring constantly. Stir in wine or broth.
5. Pour sauce over chicken and serve immediately.