This tuna sandwich is all about olive oil. Use the French stuff if possible; otherwise, any mild olive oil will do—save that fancy super-Tuscan for something else. The tuna and the bread are crucial, too. Forget about tuna packed in water. It's flavorless. You want the kind packed in olive (not vegetable) oil. We thought ortiz's Bonito del Norte, newly exported from Spain, was the closest thing to Ni‧oise tuna, but it can be tough to find. (We ordered ours from Citarella; 212-874-0384.) Of the brands commonly available in the United States, we preferred Progresso light tuna. Other brands of canned light tuna that we are fond of are Genova and La Giara. This last is very expensive—about $10—and is available at many specialty foods shops and by mail order from Citarella.
