This soup can be made a day ahead. How much artichoke you have to work with after peeling will depend on how knobbly they are to start with. The smoother they are, the less waste.
Trim off any black bits from the Jerusalem artichokes, then peel them and chop them into roughly 2.5-cm / 1-inch pieces.
Put these into a pan with the diced onion, chopped garlic and butter, and sweat the vegetables over a low heat until soft.
Add the diced potato and pour over the chicken or vegetable stock. Season with salt and pepper and bring to the boil. Lower the heat to a gentle simmer and cook for 20 minutes.
Liquidize the mixture in a blender or food processor and pass it through a sieve into a clean saucepan.
About 20 minutes before you want to serve the soup, reheat it gently, then stir in the double cream and adjust the seasoning to taste.
Serve the soup in warmed soup bowls, scattered with chopped flatleaved parsley.
© 1998 Alastair Little and Richard Whittington estate. All rights reserved.