Coat chicken with mixture of flour, sesame seeds, salt and pepper. In large skillet or slow-cooking pot with browning unit, brown chicken in oil. Add onion, celery, wine, bouillon cube, and tarragon. Cover and cook on low 6 to 8 hours. Turn control to high. Remove chicken to warm shallow dish. Dissolve cornstarch in water and stir into pot. Cook on high 15 minutes. Turn heat off; stir in sour cream. Pour sauce over chicken; serve hot.