Flake any cold cooked fish, dust it with salt, pepper and lemon juice. Rub the bottom of a bowl with the garlic, add the mayonnaise, gherkins, olives and capers. Mix and stir in the parsley. Spread a thin layer of this dressing over a plain slice of bread, do not butter the bread, cover it with fish, put on top a crisp lettuce leaf, then cover with another slice of bread that has been spread with the dressing. Press, trim the crusts and cut into fingers.