This is a juicy sandwich and your bread selection here is important. Opt for something like ciabatta or focaccia, that has a crust on top and on bottom. You can build these sandwiches individually, opening all and working through each step, or you can build them on a large single focaccia, wrap the whole thing up and slice into squares the next day. Your choice! The 4-hour or overnight rest is key, this allows the sandwich to almost marinate and makes it the ideal picnic fare.