Simple, fresh and tasty, it is a staple for breakfast or a quick lunch in southern France. Serve with or without the prosciutto.
Slice the baguettes in half lengthwise but leave them hinged, then slice them in half the opposite way to make 4 equal-sized pieces. Butter the inside of the baguettes. Assemble the sandwiches by stacking the mozzarella, tomato, lettuce, and prosciutto inside the buttered baguettes. You can use as much or as little of each ingredient as desired. Serve with Dijon mustard.