We served this soup to our lucky guests on New Year's Eve. Jersualem Artichokes are currently in season. They're nothing to with artichokes by the way: bizarrely, they're actually the tuber of a species of sunflower, Helianthus tuberosus; Winter root vegetables. They look a bit like small, knobbly potatoes, with a pinkish coloured skin, and were grown by the Native American Indians long before the arrival of the European settlers. I love their subtle, slightly earthy taste.
And there's something else about Jerusalem Artichokes you need to know: apparently they make you "windy", whatever that means. Every time some television chef mentions Jerusalem artichokes on screen, they suddenly "come over" all coy (the otherwise excellent Nigel Slater was a recent culprit), it's slightly bugging; my theory is that if you cook them well enough, you shouldn't have any problems.
Here's how I made the soup. It was velvety smooth; and utterly delicious: Chop up some an onion or two and fry gently in butter and oil with some chopped celery. In the meantime, take your Jerusalem Artichokes and using a peeler, remove the skin. You might find it easier to cut off the knobbly bits first. Plunge the peeled artichokes into a bowl of cold water into which you've given a good squeeze of lemon. This will stop your artichokes turning grey. You'll find that they start changing colour very quickly if you don't.
Chop the artichokes into small pieces, and add them to the hot pan. Stew them gently with the onions and the celery for about fifteen minutes. When they're soft, pour in some stock (I used an excellent, slightly salty ham stock), and simmer for a further twenty or so minutes.
When the artichoke pieces are cooked (ie soft), transfer the contents of the pan (the artichokes and the hot liquid) to your magimix or blender, and puree the mixture until smooth. The soup will be a creamy-white colour. Push through a sieve into a clean pan (this will help to make the soup velvety-smooth), check the seasoning (I used an oak-smoked salt from Waitrose to give the soup a slightly smokey flavour, lots of freshly grated nutmeg and some white pepper) adding a decent squeeze of lemon juice, and stir in several tablespoons of double cream to taste. Stir carefully and simmer gently for a few more minutes until hot enough.
Serve with crisp croutons and garnish with fresh dill.