I can remember my mom preparing this dish like it was yesterday. She made it especially for Lent. At home we used to not eat red meat during Lent, so during those days the dishes were made from fish, beans and chicken. The whole family loved this dish in particular, and if mom announced that she would prepare the "Fish with potato au gratin" we would all jump for joy.
I have continued the tradition and now I also prepare it at home. Not only for Lent, but also throughout the year!