Just a good, simple sandwich. The better the croissant, the better the sandwich. I used baby Swiss, but it might have been better with the stronger regular Swiss.
Heat oven to 375F. Cut a pocket in the croissant. Mix the mayonnaise and Dijon and spread on cut sides. Place the ham and cheeses in the pocket and put on a baking sheet. Bake about 10-12 minutes or until the cheeses melt. Serve hot.