On the Paris endangered eats list is the Jambon-Beurre sandwich. Nothing more than an amazing baguette (preferably the skinny ficelle) topped with slightly salted French butter and spiced Parisian ham (aka jambon de Paris), it the simplest combo but a good version of it is harder and harder to find.
Caractère de Cochon is out to right that wrong. I discovered them on the Paris episode of #OffMenu and it was love at first bite. It's a tiny shop next one of my favorite markets, the Marché des Enfants Rouges, and they do the classic sandwich right. It's so simple to make that it really doesn't require a recipe. But it does require that you get the best ingredients (preferably an epic ficelle, some demi-sel butter, and authentic Jambon de Paris) you can find!
cut into 12-inch lengths (or use mini baguettes)
salted to your liking, at room temperature
or other high-quality ham, sliced paper thin
Slice each ficelle length in half lengthwise so you have an open sandwich. Spread a ridiculous amount of the room temperature butter on the baguette then layer each with a few slices of paper-thin ham. Close and eat way too many.
Ficelle is a bread that is similar to, but much thinner (~1 1/2 to 2-inches wide), than a regular baguette. If you can't find it, use mini baguettes.