Does Your Brachah Have a Shel?

There are various customs regarding the nusach of the brachah on lighting the Chanukah menorah. Some siddurim read “l’hadlik ner shel Chanukah ” others simply say “l’hadlik ner Chanukah ” and a third group put the shel in parentheses. How did we come to have different versions of the same brachah?^[i] What is the reasoning behind each of these versions? And which one is correct? Let’s examine the sources and trace the history and halachah of this brachah.