Grate 2 teaspoons orange peel.  Halve 1 orange; squeeze to yield ½ cup juice.  (If orange doesn't have enough juice, use a second one as needed.)  Pare and slice remaining oranges; set aside.  Flatten chicken with mallet; use waxed paper to prevent splatter.  Sprinkle with pepper (and salt if desired).  Sauté chicken in 2 teaspoons oil in skillet; turning once.  Cook until done but still moist and tender.  Stack chicken at side of pan.  Add orange peel, juice, onion and mustard to pan and cook, stirring to get a sauce.  Add orange slices and pistachios and heat thoroughly. 

Serving suggestion:  This recipe can be easily multiplied for serving as an entree for entertaining.