Creamy Balsamic Chicken

1 onion, sliced
2 tablespoon butter
4 boneless chicken breasts
1/2 cup chicken broth
1 cup cream
2 tablespoons balsamic vinegar
8 ounces mushrooms, sliced
1/2 cup parmesan cheese
salt and pepper to taste

Cook the onion slices in one tablespoon of butter for about 15 minutes or until caramelized. Remove from frying pan. Add the remaining tablespoon of butter to the same pan and brown the chicken in it; remove. Deglaze the pan with the chicken broth, then stir in the cream and balsamic vinegar. Add the mushrooms and cook for a few minutes. Return the chicken to the pan and cook for 10-15 minutes or until cooked through. Remove the chicken to a platter. Stir in the Parmesan cheese and onions and pour sauce over chicken to serve. Makes 4 servings.