Some chefs say that a true salade Niçoise doesn’t contain potatoes. You may certainly omit them if you want to adhere to tradition . . . or if you are trying to lose weight. New potatoes are less starchy than their adult relatives, but they are easily replaced by radishes and green beans, if you...
Assemble, prepare, and measure ingredients. Trim beans. Halve tomatoes. Thinly slice radishes. Tear basil leaves roughly.
Place potatoes in a saucepan, cover with water, add 1 tablespoon salt, and bring to a boil over high heat. Boil for 12–15 minutes, or until fork-tender.
In a small saucepan, cover eggs with cold water and bring to a boil over high heat. Boil for about 5 minutes. Immediately remove eggs from heat, drain, and gently roll on countertop to crack shells. Peel eggs under cold running water and set aside.
Fill a large bowl with ice water. Bring a small saucepan of salted water to a boil, add beans, and blanch for about 4 minutes. Plunge into ice water to stop cooking, then drain.
For the vinaigrette, in a small bowl, whisk together vinegar and mustard. Slowly add olive oil, whisking to emulsify. Season with salt and pepper.
For the salad, arrange green beans, tomatoes, radishes, potatoes, olives, anchovies, and capers on each plate. Drizzle with some dressing. Add halved hard-boiled eggs and tuna to each plate. Scatter basil leaves over top and season with salt and pepper. Serve with extra dressing on the side.