Line a 9x13 pan with wax paper or non-stick foil.
Combine marshmallows and butter in a microwave-safe bowl or in a medium saucepan.
If microwaving, heat for 45 seconds, add Nutella, and heat for another 15-20 seconds. If on the stove, melt butter and marshmallows over medium-low heat until mostly melted, then add in Nutella and continue stirring.
Stir until smooth, then add in the Rice Krispies and salt.
Spread evenly into lined pan, let set, and cut into squares.