Rinse the mussels well, scrubbing them gently by ... The meat should remain intact and full on one half of the shell.

Blend until smooth and return the green sauce to the mussel cooking pot. Remove the empty half shell from all the mussels and add the full halves to the green sauce. Briefly reheat and serve.

Remove the mussels from the casserole one at a time. Remove half of their shells and place them, shell down, on a large baking tray. Drizzle over a little of the cooking liquor, then discard the rest.