Season the breast halves with salt & pepper and coat them with flour.
In a skillet use the butter to saute the breast halves till golden
brown on both sides. Add the onion and the mushrooms and continue
cooking for another 15 minutes. Place the chicken on the dinner
plate. Pour the wine in the skillet and, using the juices and the
scrapings, make a sauce; continue stirring and cooking it till it
forms bubbles then pour it over the chicken. Garnish with fresh
parsley and serve with steamed vegetables.