This sweet-and-sour Iranian sauce for wild duck or pheasant is also good with chicken but a little too rich for an ordinary duck. Make it in the autumn when fresh pomegranates are in season, or use the thick dark brown bottled pomegranate syrup. Be sure that the walnuts are not stale.
Brown the duck quickly in hot oil in a large heavy pan. Remove the pieces and fry the onion in the same oil until it is a rich brown, stirring occasionally. Add the walnuts which should not be too finely ground (you should be able to feel them) and cook gently, stirring often, for about 2 minutes.
To extract the juice from the pomegranates, cut in half, scoop out the seeds (discarding t