Heat the oil in a saucepan, add the shallots celery, celeriac and ginger, saute for 5 minutes, then add the pear and chestnut and sate for another 2 minutes. Add the vegetable stock and season with salt and with pepper. Bring the soup to boil, lower heat and let simmer for 20- 25 minutes or until the celery is soft.
Let cool for few minutes and using the blender puree soup.
Reheat, check for seasoning and serve.
For decoration; peel, core and slice pear and sate in a frying pan with 2 tbsp oil for 3-4 minutes in a single layer and not overcrowded. Use celery hearts for decoration too.