4 skinless, boneless chicken breast halves, about 1 1/2 lb.
Salt to taste, if desired
Freshly ground pepper to taste
1 tbsp. butter
4 tbsp. finely chopped onion
1/4 tsp. dried thyme
1 tbsp. red wine vinegar
1/4 c. dry white wine
1/2 c. fresh or canned chicken broth
2 tsp. tomato paste
1/4 c. heavy cream
1 tbsp. Dijon - style mustard
2 tsp. finely chopped parsley, optional

Sprinkle the chicken breast halves with salt and pepper. Heat the butter in a heavy skillet and add the breasts, skin side down. Cook until browned, about 6 minutes. Turn the pieces and cook about 6 minutes longer. Remove the chicken pieces to a warm platter and set aside. Add the onion and thyme to the skillet and cook briefly, stirring, until the onion is wilted. Add the vinegar and wine and bring to a boil. Add the chicken broth and bring to a boil. Stir in tomato paste. Cook until reduced by half and add the cream. Bring to a full rolling boil and stir in the mustard. Put sauce through a strainer, pressing to extract as much liquid as possible. There should be about 1/2 cup. Spoon the sauce over the chicken pieces and garnish, if desired, with parsley. Serve immediately. Yields 4 servings.