The recipe contains four ingredients that are foundations of French cuisine and have been perfected by generations of traditional production: baguette, butter, Jambon de Bayonne, and Brie. The beauty of this sandwich lies in the uncomplicated—but deeply satisfying—combination of flavors. Ingredients of the best quality will make all the difference—look for a fresh artisan baguette and a wedge of ooey-gooey Brie du Pommier. (The stronger those mushroom aromas, the better!) Herb compound butter adds a refreshing note, but plain cultured butter will do just as nicely. Agour Jambon de Bayonne is newly available in the US, but you can ask for it at your local deli or specialty shop. This French-style cured ham is extra-aged to develop deep, concentrated flavors and a sweetness that is unique and delicious.