Add the celery root and fennel and cook for 5-8 minutes, or until the vegetables are becoming soft and the fennel is slightly clear. Add the vegetable broth and salt, and bring the mixture to a boil. Lower it to a simmer, and simmer the vegetables for 15-20 minutes, or until they're very tender. Transfer the soup to a blender in batches to puree it, or use an immersion blender. Return it to the pot to keep it warm, and serve with a drizzle of
cashew cream and chive oil (recipe below), if desired.