Serve with cold poached salmon, Dublin Bay prawns, and other fish and shellfish.
1 cup mayonnaise, preferably homemade
¾ cup watercress, finely chopped
6 to 8 chives, cut into small pieces with a knife or scissors
Put 2 tablespoons of the mayonnaise into the bowl of a food processor, then add the watercress and chives. Pulse several times to obtain a rough purée.