In a 12- to 14-inch skillet, heat olive oil until smoking. Season chicken breasts with salt and pepper and place skin-side down into hot pan. Cook until skin is dark golden brown, careful not to burn the skin. Turn breasts over in skillet and add vinegar, tomato paste and butter and stir until smooth. Lower heat and simmer 8 to 10 minutes, or until chicken is cooked through. If liquid dissipates, add more balsamic vinegar. Place chicken on warm plate, pour sauce over and serve. This recipe yields 4 main course servings. Recipe Source: MOLTO MARIO with Mario Batali From the TV FOOD NETWORK - (Show # MB-5653 broadcast 04-08-1996) Downloaded from their Web-Site - http://www.foodtv.com Formatted for MasterCook by Joe Comiskey, aka MR MAD - jpmd44a@prodigy.com ~or- MAD-SQUAD@prodigy.net 09-19-1998 Recipe by: Mario Batali