Butter each piece of bread on one side, and smooth on a thin scraping of dijon mustard on each piece. Layer the sandwich so you have bread, lettuce, cheese, lettuce, and close the sandwich lid with the final piece of buttered bread.
The amount of gorgonzola cheese you put on is up to you. It's got a heavy-duty kick to it, so I'd suggest thin thin thin amounts.
Serve with Burgandy wine, some Italian olives in a side bowl (that would be the black ones usually), and a small green salad, complete with sliced cucumbers, olive oil dressing, thinly sliced red onions (sometimes known as Spanish onions).