Melt butter in heavy large saucepan over medium heat. Add celery roots, onions and celery. Sprinkle with salt and pepper. Cover and cook until tender, stirring occasionally, about 20 minutes. Add garlic, celery salt and cayenne pepper and stir 1 minute. Add vermouth and boil until most of liquid evaporates, about 8 minutes. Add stock. Bring to boil. Reduce heat and simmer until vegetables are very tender, about 15 minutes. Puree soup in blender in batches until smooth. Return to saucepan. Add cream. Simmer until thickened to desired consistency, about 5 minutes. Ladle soup into bowls. Sprinkle with chives and serve.
c.1997, M.S. Milliken & S. Feniger, all rights reserved