1. Combine flour with salt and pepper in a ziplock bag. Dredge chicken pieces in the mixture.
2. Heat oil in a large frying pan and fry the chicken pieces on both sides. Remove to a pan.
3. In the same pan, sauté the onions until golden; add sliced mushrooms and sauté until soft. Pour in Marsala wine and chicken soup and bring to a boil. Stir in chicken and simmer for five to 10 minutes, or until sauce has permeated the chicken.