Break each graham cracker square in half and spread about a teaspoons (or more!) nutella on 4 of the halves.
Top the halves with the nutella each with either a large marshmallow or about 9 minis. Set other 4 squares aside.
Place assembled s'mores on a sheet and place under broiler. Be sure to keep an eye on it as it really won't take long to start browning and then you will want to turn your sheet to evenly brown each one.
When browned to desired amount take out and top each with the remaining graham cracker halves.