Cardoon Soup

Cardoons that come from Aquila are famous throughout the entire country for their size and quality. They appear to be somewhat hard to get hold of in the UK (I wonder why? The climate is so perfect for them!), so large crispy fen celery is one substitute, or Jerusalem artichokes, or half celeriac and half Jerusalem artichokes. I have seen cardoons growing in herbaceous borders in the UK, but why not in the vegetable patch? They are such a delicious and versatile vegetable.