Scrub the mussels and discard any with broken shells, or which do not shut when tapped with a knife.

Put them into a large saucepan with the onion, wine and lemon juice. Cover and cook quickly until the mussels open, discarding any that do not.

Remove the mussels from their shells and leave to cool. Reserve the cooking liquid.

Heat the olive oil in a saucepan and add the garlic and the shallot, or spring onions. Cook gently, until golden brown.

Stir in the tomatoes, spices and herbs. Season to taste and blend in the reserved liquor from the mussels. Bring this mixture to the boil and allow to boil rapidly, until the tomatoes are soft and the liquid is reduced by half. Remove the bay leaf.

Allow the sauce to cool, then stir in the mussels. Chill well and serve garnished with black olives.