The wonderful depth of flavour in this soup comes from combining mussel cooking juices and wine then lightly enriching with a little cream.
600 grams firm white fish (I use Monkfish)
24 mussels, scrubbed
1 cup white wine
1 tablespoon olive oil
good knob of butter
1 large leek, thinly sliced
1 fennel bulb, thinly sliced, fronds reserved
sea salt and freshly ground pepper
2 cloves garlic, crushed
1 tablespoon fresh thyme leaves
good pinch of saffron threads
2½ cups chicken or vegetable stock
½ cup cream
small handful flat-leaf parsley, chopped
Put the mussels and white wine in a large saucepan over a high heat. Cover and steam until the mussels have opened. Transfer the mussels to a large bowl and strain the cooking liquids through a fine sieve into a measuring jug, discarding any sandy bits left in the bottom of the saucepan. You should have about 1½ cups of liquid.
Set 4 small mussels aside for the garnish, then remove the remaining mussels from their shells, discarding any that didn’t open. Cut each mussel in half.
Rinse out the saucepan and place back over the heat. Add the olive oil, butter, leek and fennel and season with salt and pepper. Cover and cook over a low heat for about 10 minutes or until the vegetables are very tender but not coloured, stirring occasionally. Add a splash of water if they start to catch.
Add the garlic, thyme and saffron and cook for 1 minute. Add the reserved mussel cooking liquid, stock and cream and bring to the boil. Simmer for 10 minutes. Cut the fish into large bite-sized pieces and add to the soup. Simmer for about 3 minutes or until the fish is just cooked. Take off the heat and add the parsley and chopped mussels. Taste and add salt if needed.
To serve: Divide the soup between shallow bowls and top with the reserved mussels in their shells, the fennel fronds and a grind of pepper.