Turn on your broiler.  Place two pieces of bread under the broiler just long enough to get them slightly toasty.  Now take them out of the broiler and turn them toasted side down on a cutting board or a plate.  Spread one slice with peanut butter.  Cover the other slice with sliced-up marshmallows, and place that back under the broiler on a cookie sheet.  Leave just long enough to get the marshmallows soft and starting to get brown.  NOTE: Pay Attention!!  Those things will burn black in a heartbeat!! 

Now turn off the broiler and bring out the cookie sheet.  Place the other slice of bread peanut butter side down on the marshmallows and press them together a bit.  Cut into pieces and allow them to cool a little before  you bite into them.  There are few burns more painful than something made out of sugar.  Hope you enjoy these as much as I do.