1. In a large saucepan, combine stock, pumpkin, celery, herbs and chestnuts.
2. Bring to the boil, reduce to a simmer and cook until pumpkin is tender (approximately 45 minutes).
3. Process the soup until smooth.
4. Add nutmeg, salt and pepper to taste.
5. Reheat gently and serve with a dollop of cream and topped with chives.