I have been to Paris, I ate a lot of ham and cheese sandwiches while I was there. The cold version picked up from a corner bakery on freshly baked French bread. I have never had a croque monsieur. Until tonight.
The sandwiches are baked for five minutes to heat through followed with a three minute broil to bubble and brown the top. These are best cut in half to facilitate eating, although no matter what you do, you will need additional napkins for all this cheesy goodness.
For the record, there is also a sandwich called a croque madame, which is this same sandwich with the addition of a fried egg on top after the broiling step. I am not a fan of fried eggs, but H.C. is. Perhaps I will cook this for him in the near future.