Croque Monsieur ("Crunch Mister") and Croque Madame ("Crunch Missis") are very traditional snacks in France. They are very simple to make and very good.
So, what are the classical recipes :

- Croque Monsieur is made of sandwich bread, ham and cheese.
Butter a slice of sandwich bread,
add a slice of ham then a slice of semi-soft cheese and finally cover with another slice of sandwich bread. Put in oven for 10 minutes and serve right away (the bread will toast and the cheese will melt).

- For a croque-madame, just add an egg on the bread.

Concerning the meaning of the name, the verb "croquer" means to crunch. It is difficult to say why "monsieur" or "madame", for monsieur, probably because workers were asking for a fast and hot dish in bars and cafés.