Put the mussels in a large pan with the white wine and water, place over a high heat and boil for 2-3 minutes, covered, until the shells just open, shaking the pan from time to time. Do not overcook or they will become rubbery. Leave to cool, then discard any mussels that have remained closed and shell the rest. Drain off the liquor through a fine sieve.
Heat the butter in a pan, add the onion, and sweat for 10-12 minutes. Add the cauliflower and curry powder and sweat for 5 minutes, then add the saffron. Pour in the stock and the cooking liquid from the mussels. Bring to the boil, then simmer for about 20 minutes or until the cauliflower is well cooked. Pour into a blender and blitz until smooth. Return to the pan and add the cream, anise, dill and shelled mussels. Heat gently but do not boil. Serve straight away.