Take your banana and cut a slit down the long way. Don't take off the skin. Cut it all the way down. Then fill the banana with the marshmallows and chocolate chips (according to your own taste).
Wrap the banana with tin foil. Set the whole package in the coals. Use two sticks and a hot pad or oven mit to get it out to check it--and be careful because the skin gets very hot. An adult should help with this part. When it's done and has cooled, you can put it in your camp bowl and eat it with a spoon. Mmm!