This is a fun twist of the sandwich classic, by Grace Parisi for Food and Wine Magazine. She makes this ham salad mixed with crunchy rye bread croutons and little bits of Gruyere cheese. Then she tosses it in a mustardy dressing with celery and chives. Grace likes to wrap the salad in Bibb lettuce leaves for an inside-out sandwich. You may choose to serve any way you'd like. Note: you can prepare the rye croutons in advance.