1/4 cup red-wine vinegar
2 1/2 tablespoons minced shallot
2 teaspoons Dijon mustard
1 large garlic clove, minced and mashed to a paste with 1/2 teaspoon salt
Rounded 1/2 teaspoon anchovy paste
1 cup extra-virgin olive oil
1 1/2 teaspoons minced fresh thyme
1 1/2 tablespoons finely chopped fresh basil
3/4 lb green beans (preferably haricots verts), trimmed
1 1/2 lb small (1- to 2-inch) potatoes (preferably Yukon Gold)
1 1/2 lb (1-inch-thick) tuna steaks
Vegetable oil for brushing
1/4 cup drained bottled capers (1 1/2 oz)
3/4 lb Boston lettuce (2 heads), leaves separated and large ones torn into pieces
1 pt cherry or grape tomatoes
2/3 cup Niçoise or other small brine-cured black olives
4 hard-boiled large eggs, quartered
3 tablespoons finely chopped fresh parsley and/or basil
Whisk together vinegar, shallot, mustard, garlic paste, and anchovy paste in a small bowl until combined well, then add oil in a slow stream, whisking until emulsified. Whisk in thyme, basil, and salt and pepper to taste.
Cook beans in a 4- to 6-quart pot of boiling salted water , uncovered, until crisp-tender, 3 to 4 minutes, then immediately transfer with a slotted spoon to a bowl of ice and cold water to stop cooking. Add potatoes to boiling water and simmer, uncovered, until tender, 15 to 20 minutes, then drain in a colander. Halve potatoes while still warm (peel if desired) and toss with 2 tablespoons dressing in a bowl, then cool.
Prepare grill for cooking. If using a charcoal grill, open vents on bottom of grill, then light charcoal. Charcoal fire is medium-hot when you can hold your hand 5 inches above rack for 3 to 4 seconds. If using a gas grill, preheat burners on high, covered, 10 minutes, then reduce heat to moderately high.
Brush tuna with oil and season with salt and pepper, then grill , turning over once, until browned on outside but still pink in center, 6 to 8 minutes total. Let tuna stand 3 minutes, then break into large (3-inch) pieces. Transfer tuna to a large platter and drizzle with 2 to 3 tablespoons dressing and top with capers.
Transfer potatoes to platter with tuna, reserving bowl. Drain beans and pat dry. Toss beans in bowl with 1 tablespoon dressing and salt and pepper to taste, then transfer to platter. Toss lettuce in bowl with 2 tablespoons dressing and salt and pepper to taste, then transfer to platter. Toss tomatoes in bowl with 1 tablespoon dressing and salt and pepper to taste, then transfer to platter.
Arrange olives and eggs on platter and sprinkle salad with parsley and/or basil. Serve salad with remaining dressingg on the side.