This is my father's recipe, adapted somewhat from an Elizabeth David cookbook if I remember right. He makes it with duck legs, but I decided to try it with a whole duck, making the confit slowly over the afternoon. The melting richness of the duck contrasts perfectly with the fresh spring peas. The whole duck works, although duck legs are easier to confit as turning them over is easier.
Take the duck out of the fridge and sprinkle with salt and black pepper. Leave for at least an hour, then sponge off any dampness on the skin with a paper towel.
Melt a tin of duck fat in a large casserole, and when hot add the duck, browning all over. Turn the heat down, or remove to a very low oven and, continue to cook for at least 2 hours, perferably more, checking every half hour, until the meat is tender. Meanwhile use the giblets, a onion and a bay leaf to make a little stock. Once the duck is cooked and tender take it off the heat. At this point strain off the fat and reserve for cooking at a later date. Remove the duck from the pan and place to one side. If you wish you can at this point cover the duck with the fat and keep it in the fridge for several weeks to reheat at a later date.
Dice an onion finely (or two if you have a lot of duck) and add to the pan the duck was cooked in. When the onion is cooked add a large quantity of petit pois, fresh or frozen, and the strained stock. Place the duck on top, skin side up to brown, and place in a high oven until the liquid is just beginning to bubble and the duck skin is crisp.
Season and serve with mashed potato.