Both the main ingredients for this soup turned up in the Riverford Seasons box, and were perfect together in a classic cream soup. Made the usual way - an onion softened in a little butter along with a couple of handfuls of peeled Jerusalem artichokes, chopped small. Whilst they are softening, remove the leaves from a big bunch or bag of watercress, and add the chopped watercress stalks to the softened artichokes and onions. Just cover with some vegetable stock and simmer for 15-20 minutes. Chuck in the watercress leaves, and allow to soften in the hot soup for just a minute, then blend it all together until smooth, using a hand blender if possible. If liked, stir in some single or double cream, but the artichokes are creamy enough not to need it. Just lovely. Any leftovers will lose the bright, vivid green, but will still taste delicious.