Prepare a stuffing as follows: In a pan melt 100 g (3½ oz) finely chopped pork fat then add 50 g (2 oz) butter and allow to become very hot. Place in this fat, 250 g (9 oz) duck livers seasoned with salt and pepper and sprinkled with a little chopped onion and a pinch of powdered thyme and bayleaf. Saute them very quickly and just sufficiently to seal their outside surfaces. Allow to become cool then pass through a fine sieve.
Bone out completely the inside of a Rouen duckling; remove the parson’s nose but leave the legs untouched.
Stuff it with the prepared stuffing and place in a Terrine just large enough to hold it. Sprinkle with ½ dl (2 fl oz or ¼ U.S. cup) brandy, cover with a thin slice of salt pork fat, cover with the lid and cook an Bain-marie in the oven for 40 minutes.
Meanwhile, prepare ½ dl (14 fl oz or 1¾ U.S. cups) excellent aspic jelly from the bones of the duckling and some strong veal stock.
On removing the duckling from the oven cover it in the Terrine with the prepared jelly and allow to become cold and set.