Check that all the mussels are tightly closed, wash under cold water and drain. Put into a wide saucepan and cover with a lid or a folded tea-towel. Steam open on a medium heat (this will only take 2–3 minutes). Remove the mussels from the pan just as soon as the shells open, allow to cool, remove the beards and discard the shells. Strain the mussel liquid and reserve.
Put the julienne of carrot and cucumber into a bowl of iced water and season with sea salt. Peel and dice the avocado (if using). Dilute the mayonnaise with the mussel cooking liquor to a light coating consistency.
© 2001 Darina Allen. All rights reserved.