This is an old school, slow roast duck recipe, the way your grandma might have made. If you have a store-bought duck or a really fat wild duck, this is the recipe for you.
Roasting a duck this way will give you crispy skin, much of the fat will render out, bathing the root vegetables underneath, and the whole bird will be cooked through.
This is how pretty much everyone made roast duck until relatively recently, when the glories of duck served medium or medium-rare began to be more well-known. Yes, you can absolutely serve duck — or goose — rare, or even raw, if it’s of good quality. Food-borne illnesses from waterfowl are very, very rare, unlike with chickens and turkeys.
So if you happen to have a wild duck, or a lean farmed duck — Indian runners and Muscovy ducks can sometimes be quite lean — you are better off using my other recipe for roast duck, which is geared specifically for lean, and wild birds.
This method, slow roast duck, is the way all of Europe has been doing it for millennia, so there’s some history here. I go into it in more detail in my cookbook Duck, Duck, Goose: The Ultimate Guide to Cooking Waterfowl, Both Farmed and Wild, an entire cookbook dedicated to waterfowl. 
The reason it works is fat. Fat is an insulator, and in a duck it’s all underneath the skin. You need to render that fat or the skin will never get crispy. And rendering fat from an obese duck takes time — so much time that your breast meat will be fully cooked by the time it’s ready (The legs and wings will be perfect, though).
I should tell you that I don’t love fully cooked breast meat; I prefer it medium-rare. It gets a bit livery and, at least to my mind, essentially becomes a vehicle for gravy.
You can do two things about this: You can slice off the breasts when they reach an internal temperature of about 135°F, then sear just the skin side in a pan before serving, or you can live with fully cooked breast meat and make a damn good gravy. (Follow the technique for the gravy in my poached turkey recipe, only subbing in duck or goose bits.)
Even fully cooked, the breast meat will still be moist because it’s been bathed in its own fat for an hour or more, so it’s not as if it will be inedible. And some people prefer it that way.
A few tips: Do not cover your duck when roasting because you want that crispy skin. If you cover it, the bird will steam.
And, you will know a roast duck is ready when the legs feel loose, the fat runs clear, and the skin is crispy.
With this recipe, err on cooking the bird longer, not shorter. As the cook, remember that the legs and wings will be the best parts. Distribute them accordingly.
My advice for when you make roast duck this way is to roast them over the top of lots of root vegetables, the more varied the better. And think about a gravy or a sauce to go with it. I have a large selection of wild game sauces here you can choose from. Other than the gravy I mentioned above, I might suggest the maple-bourbon gravy for starters…
Slow Roast Duck
Ingredients
- 1 domesticated duck or 2 very fat wild ducks (see above)
- 1 tablespoon kosher salt
- 1 lemon, cut in half
- 4 sprigs sage, rosemary, parsley or thyme
Instructions
- Set your oven to 325°F. Using a needle or a sharp knife point, prick the skin of the duck all over -- but be sure to not pierce the meat itself, only the skin. This lets the fat render out and will help crisp the skin. Pay special attention to the back, the flanks, and the very front of the breast.
- Rub the cut lemon all over the duck and stick it inside the cavity. Liberally salt the bird; use a little more salt than you think you need. Stuff the duck with the herbs. Let the bird sit out for about 30 minutes to come to room temperature, while the oven heats up.
- When you are ready to roast, put the duck in an iron frying pan or other ovenproof pan and surround it with root vegetables. Set the pan in the oven. Small ducks (wood ducks, wigeon, teal, ruddies, etc.) only need 40 minutes in the oven. If you are roasting mallards or a typical, store-bought Pekin duck, you will want to increase the roasting time to 90 minutes. A goose may take as long as 2 hours. After the allotted time, take the pan out of the oven and set the ducks on a cutting board to rest. Spoon any fat that has accumulated over the vegetables and salt them well. If the veggies are ready to eat, remove them. If there is a lot of excess fat, spoon it off.
- Now increase the heat to 450°F. When the oven hits this temperature, return the birds to the oven and roast them for up to 30 more minutes, or until the skin is crisp. The reason you take the bird out of the oven is because a) the resting time helps redistribute the juices in the bird midstream, and b) you are crisping skin without totally overcooking the duck by only returning it to the oven when it is hot.
- Remove from oven and let the birds rest. Small ducks need 5 minutes resting time, large ducks 10 minutes, geese 15.
