In a shallow nonporous dish or bowl combine the salsa, mustard and lime juice. Mix well. Add chicken, cover dish and refrigerate. Marinate for at least 30 minutes.
Melt butter or margarine in a large skillet over medium heat. Remove chicken from marinade and add to skillet. Saute, turning frequently, until browned on all sides.
Meanwhile, boil remaining marinade in a saucepan for 4 to 5 minutes, to remove all possibility of bacteria. Add boiled marinade to chicken and saute another 3 to 5 minutes or until chicken is 'fork tender' and marinade is starting to glaze. Remove chicken to serving platter; raise heat to high and boil marinade for 1 minute.
Spoon marinade over chicken and top each breast with 1 tablespoon yogurt and 1 lime wedge. Serve.