1 5 1/2-pound duckling or 3 1-pound duck breasts (magrets)
1/4 cup flat-leaf parsley leaves
2 large cloves garlic
1/2 cup panko
Salt and freshly ground black pepper
1 tablespoon duck fat or extra virgin olive oil
1 large sweet onion, sliced thin
1 1/2 tablespoons Dijon mustard
2 tablespoons dry red wine
6 hamburger buns, preferably brioche
Bone whole duck, discarding all skin and bones and keeping fat. Kitchen shears and a sharp knife are best for this. Cut meat with fat in 1-inch cubes. If using magrets, remove skin and fat, reserving fat. Dice meat. Dice enough fat to make 1 1/3 cups, about 6 ounces.
Place parsley in food processor and process to chop fine. With machine running, drop garlic through feed tube to mince. Add duck meat and fat, and pulse until finely and uniformly chopped. This will take 35 to 40 quick pulses. Remove contents of processor to a bowl, add panko and season with salt and pepper. Form into 6 patties. Refrigerate.
Preheat a grill, preferably charcoal, or a broiler, to very hot. Place duck fat or oil in a skillet. Add onion and sauté over medium-low heat until tender and golden. Stir in mustard and wine and season with salt and pepper. Set aside.
Grill or broil patties until medium-rare to medium, about 3 minutes a side, depending on heat. Toast buns. Reheat onion mixture, use to top burgers and serve with buns.