Clean the mushrooms with a cloth or brush (do not wash them or the flavour disappears).
Roughly chop any large mushrooms and leave the smaller ones intact.
Put the water, lemon juice and some salt into a saucepan.
Bring to the boil and add the mushrooms.
Simmer for approximately four minutes.
Meanwhile, in a bowl, combine the olive oil, garlic, parsley and olives.
Drain the mushrooms and add immediately to the olive oil marinade.
Mix well, check for seasoning and leave to cool.
Serve with lemon wedges.