Place rice krispie cereal in a large mixing bowl and set aside.
In a saucepan over low heat, melt the butter. Once melted, add the mini marshmallows, stirring constantly until they're fully melted and the mixture is smooth.
Mix in the nutella until smooth, then remove the saucepan from heat.
Pour the marshmallow mixture over the rice krispies and stir until well combined.
Transfer the mixture to a lightly greased 8x8-inch pan. Press down evenly using a piece of wax or parchment paper.
Allow to cool completely. To expedite the cooling, you can place them in the fridge for about 5 minutes.