By Victoria Alexander and Genevieve Harris
You can substitute potatoes for the Jerusalem artichokes. The best potatoes to use are low starch, white-fleshed varieties, such as pontiacs (round red potatoes). If you have an abundance of oysters, you can add some to the finished soup just before serving.
PEEL AND ROUGHLY chop the artichokes and onion. Melt the butter in a large saucepan over a low heat, add the artichokes and onion and cook until the onion is soft and translucent, about 5–8 minutes. Wash the oysters in the water to remove any grit. Take out the oysters and strain the remaining liquid through a fine sieve. Add the oysters to the saucepan and cook for 2 minutes. Add the re