Prepare couscous following packet directions. Place in a large bowl.
Cook beans in a small saucepan of boiling salted water for 2 minutes or until just tender. Drain and cool in ice water. Drain.
Heat half the oil in a large frying pan over medium-high heat. Season chicken and cook for 2 minutes each side or until golden and cooked through. Remove pan from heat and add lemon juice and tarragon. Toss to coat and stand for 3 minutes. Slice and add to couscous with any pan juices. Add beans, kale, tomatoes and remaining oil. Season and toss to coat. Serve.