Step 1 Wash and dry the lettuce. Wrap it in a towel and place it in the refrigerator.
Step 2 Peel and grate the carrots on the medium hole of a box grater. Place in a bowl, add the chervil and dress with 4 teaspoons lemon juice, 2 tablespoons and 2 teaspoons olive oil, salt and white pepper to taste. Set aside.
Step 3Drop the tomatoes into boiling water. After 10 seconds, drain and shock in ice water. Using a small paring knife, pull the skin off each tomato. Place the peeled tomatoes in a medium bowl. Peel and seed the cucumber, cut in half lengthwise, and slice into half-moons about one-fourth-inch thick. Add the cucumber to the tomatoes, along with the garlic, one-half teaspoon red wine vinegar, one-eighth teaspoon salt, black pepper to taste and 1 tablespoon olive oil. Toss gently and set aside.
Step 4Drain the tuna and flake it into a medium bowl. Drain the cannellini beans, rinse them briefly in a colander, and add them to the tuna. Add the sliced red onion, the parsley, 1 tablespoon lemon juice, one-half teaspoon red wine vinegar, 1 tablespoon olive oil and black pepper to taste. Set aside.
Step 5Mix a little extra vinaigrette: Whisk a pinch of salt into 1 1/2 tablespoons vinegar. Whisk in 3 tablespoons olive oil and add black pepper to taste.
Step 6On four individual plates, arrange a bed of lettuce, tearing the leaves if desired. In the center of each, mound one-fourth of the cannellini-tuna mixture. Next to that, spoon one-fourth of the tomato-cucumber salad, and on the other side, one-fourth of the carrots. Place a few olives strategically next to the tomato-cucumber salad. Drizzle a little vinaigrette over the greens and serve immediately.