1. Place the chicken in a single layer in a shallow glass or ceramic dish and pour the marinade over it, turning a few times to coat. Cover and refrigerate for at least 1 hour and as long as 6 hours.
2. Put the potatoes in a saucepan and add cold water to cover by several inches. Bring to a boil over high heat and cook for 10 to 12 minutes just until fork tender. Drain and cool. Do not overcook.
3. Blanch the haricots verts in boiling water to cover for about 1 minute. Drain and cool.
4. Prepare a charcoal or gas grill. Lightly spray the grill rack with vegetable oil cooking spray. The coals should be moderately hot.
5. To make the vinaigrette, in a small bowl, whisk together the olive oil, vinegar, shallots, mustard, and tarragon. Season to taste with salt and pepper. Set aside.
6. Lift the chicken from the marinade. Discard the marinade. Grill the chicken for 12 to 16 minutes, turning several times, until cooked through. Slice into thin strips.
7. Thread the potatoes on metal skewers and grill for about 5 minutes until lightly browned. Cut into halves or quarters, depending on their size. Transfer to a bowl and toss with about 5 tablespoons of vinaigrette.
8. Meanwhile, in a separate bowl, toss the haricots verts with 3 or 4 tablespoons of vinaigrette. In another bowl, toss the cherry tomatoes with 3 or 4 tablespoons of vinaigrette.
9. Assemble the salad by spreading the beans on a platter. Top the beans with the potatoes and then the chicken. Arrange the tomatoes around the chicken and sprinkle the salad with tarragon. Drizzle a little vinaigrette over the salad and serve.