Grilled Chicken Salad with Radishes, Cucumbers, and Tarragon Pesto

Place 1/4 cup tarragon leaves, parsley, 2 tablespoons pine nuts, 1 teaspoon lemon juice, and shallot in mini processor; chop coarsely. With machine running, gradually add 3 tablespoons olive oil. Season pesto to taste with salt and pepper. Add more olive oil by teaspoonfuls to thin, if necessary. Whisk 2 teaspoons chopped tarragon, remaining 4 teaspoons lemon juice, and 3 tablespoons oil in small bowl. Season dressing with salt and pepper. Prepare barbecue (medium-high heat). Brush chicken breasts on both sides with oil. Sprinkle with salt and pepper. Grill until grill marks form, skin is crisp, and chicken is cooked through, 7 to 8 minutes per side. Transfer to work surface; let rest 5 minutes. Using clean brush, brush both sides of bread with oil. Sprinkle with salt and pepper. Grill until dark-brown grill marks appear on both sides, 2 to 3 minutes per side. Place greens, radishes, and cucumbers in large bowl. Toss with dressing. Season to taste with salt and pepper. Divide salad among 4 plates. Cut grilled chicken breasts crosswise into 1/3-inch-thick slices. Arrange 1 sliced chicken breast atop salad on each plate. Spoon tarragon pesto over chicken. Sprinkle remaining 2 tablespoons pine nuts over salads. Serve with grilled bread slices.