A smooth soup made from jerusalem artichokes, onions, garlic, celery and stock.
1 Heat the butter in a soup pot over medium-high heat and cook the onions and celery until soft, about 5 minutes. Do not brown them. Add the garlic and sauté for 1 minute. Sprinkle with salt.
2 Add the jerusalem artichokes and the chicken stock to the pot and bring to a simmer. Reduce the heat to low, and simmer, covered, until the jerusalem artichokes begin to break down, 45 minutes to an hour.
3 Using an immersion blender or upright blender, purée the soup. If using an upright blender, fill the blender bowl up only to a third of capacity at a time, if the soup is hot, and hold down the lid while blending. Alternately, you can push the soup through the finest grate on a food mill, or push it through a sturdy sieve. Add salt to taste.
Sprinkle with freshly grated black pepper to serve.