1 French baguette (about 26 inches long)
3 tablespoons butter, at room temperature
3 tablespoons Dijon mustard
8 ounces unsmoked and very thinly sliced deli ham
8 ounces very thinly sliced Gruyère cheese
10 cornichons, thinly sliced lengthwise
Halve the baguette lengthwise. Spread one cut side with the butter, and the other cut side with the mustard. Layer the ham, cheese, and cornichons on the bottom half of the baguette. Close the sandwich with the top half of the baguette and press down lightly. Cut crosswise into 4 equal portions, each about 6 inches in length. Serve immediately.