The refreshing combination of ingredients and textures with a mix of briny and oily, contrasts with a light citrus dressing. The ingredients are “composed” or separated out on a plate or platter rather than tossed together.
In a small bowl whisk together the oil, basil, lemon juice, and Dijon, then season to taste with salt and pepper. Set aside until ready to use.
Bring a medium pot of salted water to a boil over high heat. Carefully add the eggs and cook for 7 minutes. Use a slotted spoon to transfer the eggs to a bowl of ice water, keeping the pot over high heat. Chill the eggs until cold then peel and set aside.
Add the green beans and potatoes to the boiling water. Cook the green beans until bright green and tender, about 2 minutes. Remove with tongs to a bowl of ice water until chilled then drain and set aside.
Continue to boil the potatoes until tender, about 15 minutes. Drain the potatoes. In a medium bowl toss the potatoes and green beans with half the dressing.
Arrange the mixed greens on a platter and arrange the green beans and potatoes in sections on top followed by the red onions, tomatoes, olives, tuna and anchovies. Drizzle the remaining dressing over the top and serve immediately.