Celery Leaves is a highly unused ingredient. Although the stalks of the celery plant are usually treated as a vegetable, the leaves of the same plant are often used as an herb. The leaves form the foundation of many traditional dishes, such as anguilles au vert. Celery leaves have the rare ability among herbs to retain much of their flavour even after prolonged cooking. Subsequently, they are often added to soups, stews, and bean dishes.