How to Make It
Preheat the oven to 450°. Cut off the first two wing joints of the ducks and reserve. Chop the necks into 2-inch lengths.
Prick the ducks around the thighs, backs and breasts. Season the ducks inside and out with salt and pepper. Set a rack in a very large roasting pan. Set the ducks breast up on the rack as far apart as possible. Add the water to the pan and roast the ducks in the center of the oven for 20 minutes. Turn the oven temperature down to 350°. Turn the ducks on their sides, propping them up by placing 2 large balls of foil between them, and roast for 30 minutes. Turn the ducks to their other sides and roast for 30 minutes longer.
Meanwhile, in a large saucepan, heat the oil. Add the hearts, gizzards, wing joints and necks and season with salt and pepper. Cook over moderately high heat, stirring, until richly browned, 10 minutes. Add the carrots, tomatoes, celery, leek, onion, garlic, bay leaves and thyme and cook, stirring, until softened, 5 minutes. Stir in the flour and tomato paste, then gradually stir in the stock and wine. Bring to a boil, stirring, then reduce the heat to moderately low and simmer for 1 hour. Strain the sauce into a bowl, pressing on the solids.
Meanwhile, remove the zest in strips from 1 of the oranges. Cut the zest into a very fine julienne. In a small saucepan of boiling water, blanch the julienne for 1 minute. Drain and rinse under cold water; pat dry.
Halve and squeeze 2 of the oranges; you will need 1 cup of juice. Peel the remaining oranges (including the one you stripped the zest from) with a knife, removing all of the bitter white pith. Cut in between the membranes to release the sections into a bowl.
In a medium saucepan, boil the sugar and vinegar over moderately high heat until the syrup is a pale caramel color, 4 minutes. Gradually add the 1 cup of orange juice, then the currant jelly and bring to a boil. Add the strained duck sauce and simmer over moderate heat to reduce slightly, 8 minutes. Season with salt and pepper. Add the Grand Marnier and remove from the heat. Swirl in the butter, 1 tablespoon at a time.
Pour off the fat in the roasting pan. Turn the ducks, breasts sides up, and roast for 40 minutes longer. Remove the ducks from the oven and preheat the broiler. Broil the ducks 6 inches from the heat, rotating the pan a few times, until richly browned, about 3 minutes.
Insert a wooden spoon into the cavities and tilt the ducks, letting the juices run into the pan. Transfer the ducks to a platter and keep warm. Scrape the pan juices into a fat separator and pour the juices back into the roasting pan. Simmer over moderate heat, scraping up any browned bits and coagulated juices. Strain the contents of the roasting pan into the orange sauce.
Garnish the duck platter with the reserved orange sections and scatter the blanched zest over the ducks. Carve the ducks at the table and pass the sauce separately.