Wash and thoroughly drain the salad leaves and place in a bowl; Cut the tomatoes in half. Add the potatoes, tomatoes and eggs by arranging them around the outside of the bowl
Break the tuna into several pieces and add to the bowl
If using cornichon, slice lengthways. Cut the olives in half. Sprinkle over the dish
Thoroughly whisk olive oil (2 parts) and vinegar (1 part) into a vinaigrette and sprinkle a little over the salad. Keep the remainder for serving at the table for those that would like extra.