1/4 cup chopped fresh cilantro
Purée first 7 ingredients in processor. With machine running, gradually add oil through feed tube and process until blended.
Place chicken in 13×9×2-inch glass baking dish. Pour yogurt mixture over chicken; turn to coat. Cover and refrigerate 1 hour.
Prepare grill (medium heat). Place chicken on grill. Cover and grill until chicken is cooked through, turning every 5 minutes, about 15 minutes total. Meanwhile, cook couscous according to package directions. Once cooked, fluff with fork and add chopped mango, the reserved herb mixture, and cilantro and stir until mixed together. Arrange chicken on large platter and serve mango couscous alongside.