I have since seen similar ideas online using Halloween Bat cookie cutters. I, personally, rarely use cookie cutters, except for my FAVORITE little star one, and occasionally some others. I really like to hand cut shapes myself.
I would think that if you grill an open-faced grilled cheese, then toast the top bread separately, and cookie cut from the toast, you may get that "window" into the sandwich I was trying to do at first. I don't know, I never went back and tried that technique, but maybe you can tell me if you have!