In a small bowl, whisk together shallot, Dijon mustard, lemon juice, salt, and pepper.
Whisk in olive oil; set aside. Divide chopped romaine lettuce leaves, red potatoes, white, eggs, green beans, tomatoes, nioise olives, and caper berries among 4 salad bowls; drizzle each with about 2 1/2 tablespoons dressing.