I admit that this terrine is labor-intensive, but you can start a day or two ahead of time and break the work up into stages. It is a derivative of a famous French dish, jambon persillé, in which ham is layered in a terrine with its congealed poaching liquid and plenty of chopped fresh parsley.
Cut up the ducks as described. Save the fat in the freezer for making confit, and reserve the breasts and legs in the refrigerator. Cut the backs and the wings into three sections each with a heavy cleaver. Roast them in a roasting pan in an oven set at 425°F, with two of t