1. Place the celery, onion and leeks into a pot with the butter allow the vegetables to sweat.
2. Once the vegetables have sweated for a few minutes add the flour and stir well.
3. Add the chicken stock bit by bit mixing well.
4. When the stock is added, add the turnip.
5. Simmer for about 15 minutes until the turnip is tender.
6. Remove from the heat.
7. Using a blender, blend the soup until smooth.
8. Pass through a sieve to catch any remaining lumps.
9. Put back on the heat for about 5 minutes, salt/pepper to taste, adding cream as required.