I have cooked sandwiches this way while camping, throw the whole thing into a heavy duty foil wrap and onto a cast iron griddle. They do burn if you are not on low heat. No need to finish on the fire, just make sure you brush a little oil on the foil first, it toasts up really nice. Last year, we did them on the fire grate over an old campfire ring, took about 10 minutes, maybe 15, one flip. It was delicious.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"I'm Armenian...perhaps...but then again...maybe not..."