Scrub mussels clean in several changes of fresh water and pull off beards. Discard any mussels that are cracked or do not close tightly when tapped. Put mussels into a saucepan with wine and water. Cover and cook over high heat, shaking pan frequently, 6-7 minutes or until shells open. Remove mussels, discarding any which remain closed. Strain liquid through a fine sieve and reserve.
Heat butter and oil in a saucepan. Add onion, garlic, leek and fenugreek and cook gently 5 minutes. Stir in flour and cook 1 minute. Add saffron mixture, 2-1/2 cups of reserved cooking liquid and chicken stock. Bring to a boil, cover and simmer gently 15 minutes. Meanwhile, keep 8 mussels in shells and remove remaining mussels from shells. Add all mussels to soup and stir in chopped parsley, salt, pepper and cream. Heat through 2-3 minutes. Garnish with parsley sprigs, if desired, and serve hot.