croque-monsieur a popular French snack, consists of a thick slice of gruyère cheese and a thin slice of ham sandwiched between layers of buttered bread and then toasted on both sides until the cheese has completely melted. Croque-monsieur can also be prepared by frying the sandwich on both sides in butter until crisp. Sometimes the sandwich is dipped in egg and breadcrumbed before frying.
Croque-monsieur literally means ‘crunch-sir’ or ‘munch-sir’ (croquer being the French verb ‘to crunch’ or ‘to munch’), but where the term originally comes from is not clear. It first appeared on French menus early in the 20th century.