1. Peel the celery root, onion and potatoes, finely chop. Wash the stalked celery, cut into pieces. Heat oil in a saucepan, add celery stalks and cook for 3 minutes. 2. Add onion, cook 3 minutes. Then put the celery root and potatoes, mix. Pour in chicken broth, add thyme. Bring to a boil, reduce heat and simmer for 20 minutes. Pour the soup into a blender, puree until smooth. 3. Return the soup to the pot, add the cream. Salt, pepper to taste. Heat up and serve.