Step 1

In a large saucepan, cover the potatoes with 1 inch of cold water, salt the water and bring to a boil over medium-high. Cook the potatoes until just tender, 8 to 10 minutes. Using a slotted spoon, transfer to a plate and let cool. Prepare a large bowl of ice water to cool the green beans. Add the green beans to the boiling water; cook until crisp-tender, about 3 minutes; drain. Transfer to the ice water to cool; drain. Slice the potatoes.

Step 2

In a small saucepan, cover the eggs with cold water; bring to a boil. Remove from the heat, cover and let stand 12 minutes. Crack the eggs all over, then soak in cold water 5 minutes to loosen the shells. Peel and quarter the eggs.

Step 3

Heat a large cast-iron skillet or a heavy nonstick pan over medium-high to high.

Step 4

Arrange the lettuces on plates or a platter. In a large bowl, toss the tomatoes, radishes, scallions and olives. Top the lettuces with the potatoes, green beans and the radish mixture; sprinkle with tarragon.

Step 5

Drizzle the tuna steaks with oil; season with salt, pepper and herbes de Provence. Add to the skillet and cook 2 minutes per side for pink centers and 3 minutes per side for opaque centers. Slice and arrange on the salad.

Step 6

On a cutting board, finely chop the anchovies. Grate the garlic over the anchovies. Using the flat side of a large knife, smear the mixture across the cutting board until a paste forms; transfer to a small bowl. Grate in the shallot, then whisk in the vinegar and mustard; gradually whisk in the EVOO in a slow, steady stream. Season. Pour over the salad.