Grease a 9x13" pan well and set aside.
In a large pot, melt the butter oven medium heat. Add the marshmallows and stir until smooth and melted. Stir in crisped rice cereal.
Remove from heat, fold in chocolate chips and then transfer to the prepared pan. Using a greased spatula, pat down evenly.
Let cool completely before cutting into squares. Store in an airtight container.