Peel and roughly chop the vegetables. Place in a large pan with the bay leaf and caraway seeds.
Cover with the stock. Bring to a rapid boil. Cover the pan and reduce the heat to a simmer and cook for about 1 hour or until the vegetables are tender.
Remove the bay leaf and liquidise the soup until smooth, adjust the seasoning. Pass the soup through a medium sieve.
Reheat gently, do not allow to boil, serve with the soured cream and Pirags.