Heat the butter in a large saucepan over a medium heat. Add the onion and celery and saute gently for 5 minutes taking care to soften but not colour the vegetables.
Add the garlic and saute gently for a further minute, before adding the Jerusalem artichoke and vegetable stock to the saucepan. Turn the heat down and simmer gently until the vegetables are soft.
Using a stick blender blitz the soup to a fine puree. Stir through the cream and season with salt and pepper to taste. Serve hot with crusty bread.
Jerusalem artichokes are a seasonal vegetable, abundant in the Winter months. However this soup does freeze really well if you want to prolong the season.Once peeled, these gnarly tubers oxidise really quickly, so if not cooking with straight away, place in a bowl of cold water with a squeeze of lemon. This will stop them going brown.