The croque-monsieur is a classic french grilled cheese sandwich that's a mainstay of parisian cafes, bars, and bistros, not to mention innumerable take-out counters. Served with a side of french fries and a little pile of salad greens, a croque-monsieur is everything that's great about eating in pariseven their snacks are somehow sublime and otherworldly. Combining a creamy bchamel sauce with nutty gruyre cheese, the croque-monsieur is grilled cheese perfection. Keep in mind that most places that serve croque-monsieurs have stacks of the things made ahead of time, and they'll warm one up for you when you order it. And yet they're still delicious. The recipe that follows will make one sandwich, but you can double it to make two. You can substitute jarlsberg or even monterey jack for the gruyre. In case you were wondering, croque-monsieur translates literally to "Mr. Crunch. " Best name for a sandwich ever.