(Optional) Preheat your pie irons over the fire while getting your supplies ready.
Butter the insides of your pie irons.
Spread one side of each slice of bread with Nutella.
Insert one half of the bread, Nutella side up, in your pie irons.
Place a handful of miniature marshmallows on top of the Nutella.
Place other slice of bread, Nutella side down, on top of the marshmallows.
Close pie iron carefully and place over campfire.
Cook over fire, flipping occasionally, until bread is toasted and marshmallows have melted. Time needed will depend on how hot your fire is.