Sauerbraten
From OSR
This is traditionally made with beef, but I made it with duck legs and it was great. Leave the skin on when roasting the duck legs (or other fatty fowl) and remove after roasting, before glazing with the sauce.
First marinate the meat in a mixture of sweet and sour ingredients with spices. My particular favorite combination is:
You can leave it to marinate for up to 2 or 3 days. Remove the meat from the marinade and roast the meat. Remove the meat from the pan. Spoon off excess fat from the pan, sprinkle with a little flour, and stir over heat to make a roux. Add the marinade to the pan and cook until it is of the desired consistency. Put the meat back in the pan and coat with the sauce, then remove and carve or serve as you like. Strain the sauce and pour over the servings of meat.