Boil or steam the potatoes. Poach the white fish gently in the wine, water and bay leaf. Do not overcook.
Make the aioli by crushing the garlic, adding the egg yolk and seasoning, then adding the oil drop by drop until the sauce amalgamates and thickens. Add the lemon juice to taste.
Put the lettuce leaves on the bottom of the serving dish, then the fish and shellfish, the potatoes and finally the onion and olives. Spoon the aioli in the centre and serve.