Roast duck is a dish that I will never ever toy with. I don't do it à l'orange, I won't toss in exotic spices such as star anise or Chinese five spice powder. The most exotic I will ever get with my roast duck is to pop an apple and maybe an onion in its belly. It's a shame, but I just can't. This is because the only reason I ever roast a duck is in order to have a duck carcass for making duck soup.
My Austrian grandmother made the best soups I have ever tasted. And of these soups, her best was cream of mushroom soup made with a duck base. It was sublime. Something about the duck broth brought out the delicate flavour of mushrooms like no other liquid. Salty and creamy and savory and delicious. You can judge how delicious the soup was by the fact that even as a child, I recognized this was pure genius.
And so when I roast a duck it's because I intend to try my best to reproduce my grandmother's best dish. Exotic spices might carry over to the broth and so they are off the menu.
It's a roundabout way to make a soup but it's the best way. I've seen a lot of cookbooks (my beloved Fanny Farmer, for one) and many cooking programs counsel boiling a raw bird with a load of vegetables in order to make a bouillon. Well, if you want watery, bland broth and a lot of soggy meat, please do. I did. Once. And then I remembered my grandmother saving the bones from roast birds and realized that the thrifty way to make chicken or duck broth is also the tasty way. Why don't any cookbooks tell you this?? Is it for fear that no one will ever make soup because it sounds like too much work? Who knows. All I know is that it's worthwhile roasting a duck (which is a nice dish on its own, too) in order to get duck broth.
So, first buy your duck. Rinse it and pat it dry. Cut up an apple and an onion in large chunks and toss them in the cavity of the bird. Sprinkle a little Lawry's salt on the outside of the bird. Prick the skin all over so that the fat will run off more easily. (There will be a lot.) Toss a glass of white wine or sherry over the bird and put it in a very hot oven for 20 minutes (Around 220C/450f). Reduce the heat and continue to roast until a meat thermometer tells you it's done. For a small bird, this will be about an hour and a half, the same as a chicken.
The duck will be fragrant and juicy from all the fat, albeit a pain to carve because of the same. I am always surprised how little meat there is on one bird; it's really only enough for two.
When you are done with the duck, toss all the bones, bits of fat and skin and juices in a large pot and cover with water. If you like, you can add a couple of potatoes and carrots and onions too. I usually do if I have any that are getting towards the end of their shelf life. I don't bother with celery. (Another mystery in my life is why most traditional cookbooks in the US tell you to add celery to soup broth.) Bring the mixture to a boil and then turn down to a slow bubble. Let it simmer for several hours, stirring it and breaking up the bones with a wooden spoon every half hour or so. When the broth has gone nice and brown and nutty and it smells delicious, pour the mixture into a colander or strainer held over a large bowl. Put the strained broth in the refrigerator for several hours, preferably overnight. Once the broth has cooled completely, the fat will rise to the top and you can skim it off with a large spoon.
You can do anything with this nectar, but my favourite thing is to combine it with cream and mushrooms. One bird will probably give you enough broth for four to six bowls of soup. So take about two pounds of mushrooms (either plain white ones or a mix of exotic ones) and sauté them in a knob of butter with a finely chopped onion or six chopped shallots. When they are soft and tasty, add the duck broth. Add a couple of generous spoonfuls of crème fraîche or, if you are in the US, a mixture of cream and sour cream. You want the tang from the sour cream or crème fraîche as it compliments the duck deliciously. Taste for salt and pepper; it will be the better for a generous helping of each.
It really is my favourite soup. It's not overly pretty (cream soups rarely are) but when you smell it you'll understand why it's my favourite soup. Even my Critic, who theoretically doesn't like mushrooms, loves this soup. Quack!
(Does anyone out there have any idea why the Marx brothers called their film Duck Soup??)