The day before, clean the duck, remove the excess visible fat, and refrigerate, uncovered overnight. Preheat your oven to 475° F.
Remove the duck from your refrigerator, then prick the skin all over using a fork, without piercing the meat.
In a suitably sized bowl, combine the 2 peeled tangerines with the sugar, and mash them using a fork until the sugar is well mixed. Lift the skin of the duck away from the breast meat, and pack the pulp under each breast.
Cut the single tangerine in half, and rub the skin of the duck all over with the cut sides of the fruit.
Squeeze out the remaining juices from the tangerine halves, add to the tangerine and sugar mash and stuff the tangerine halves into the duck cavity. Pour the remaining tangerine and sugar mixture into and over the duck.
Stuff the duck cavity with the chopped onions, chopped celery, and bay leaves. Sprinkle the salt and pepper over the duck and inside the cavity of the duck, rub well into the skin.
Place the duck in a roasting pan with a rack, and sprinkle the tangerine peel around the duck.
Roast the duck for 20 minutes, then reduce heat to 350° F and roast for 35 minutes.
Turn the temperature up to 475° F and roast until very dark and crisp (about 20 minutes).
Servings: 4