Step 1 Heat the oven to 350 degrees. Grind the peppercorns, allspice and cloves to a fine powder in a spice grinder.
Step 2 Rinse the duck legs and pat them dry. Cut away the backbone, if it is still attached (there's almost no meat, but lots of bones). Lightly score the skin on both sides, cutting through the skin but not completely through the fat. Season liberally with salt and the spice mixture; rub it in.
Step 3Heat the oil in a large skillet over medium heat. When the oil is hot, add the duck legs, skin side down. Cook until quite brown, about 15 minutes, and then turn and cook the other side. The duck will stick at first, but the skin will release with a gentle jiggle when it has browned enough, so don't force it. Also, don't rush the process; in addition to browning the skin, this step renders a lot of fat. Because duck legs are quite large, you may need to do this in two steps or in two pans.
Step 4While the duck legs are browning and after they've rendered some of the fat, spoon about 3 tablespoons of the fat into the bottom of a large, heavy braising pan. Add the onion and cook over medium heat until soft, about 5 minutes. Add the shallot and cook another 3 or 4 minutes. Remove from heat and set aside until the duck legs are done.
Step 5When the duck legs have browned on both sides, transfer them to the braising pan, arranging them on top of the onions, with the "knees" facing the center. They may overlap slightly. Add the red wine, balsamic vinegar, beef stock and orange zest and bring to a gentle simmer. Place a sheet of aluminum foil over the legs, pressing lightly to minimize the amount of air. Cover and place in the oven for 30 minutes.
Step 6While the legs are cooking, peel, quarter and core the quince. Slice each quarter crosswise into 2 pieces.
Step 7When the duck legs have braised for 30 minutes, remove them from the oven. If there is fat floating on the surface of the liquid, skim as much as you can with a large spoon. Place the quince on top of the duck and give the pan a shake to settle them into the liquid. Season the braising liquid with salt to taste. Replace the foil and the lid and continue cooking until the duck is tender enough to be easily penetrated with a skewer and the quince is quite soft, about 40 to 45 minutes.
Step 8Gently stir in the dried sour cherries, replace the lid and let stand at room temperature until they soften slightly, about 5 minutes. Sprinkle with the minced parsley and serve immediately.