1Spray a 9x13-inch dish with nonstick cooking spray.
2In a large pot over medium heat, melt butter with marshmallows. Stir frequently and melt gently until smooth and combined. Do not allow to burn.
3Take pot off heat. Stir in the cereal until mixture is combined. Stir in chocolate chips. They will melt as you stir them in. Pour mixture into prepared baking dish and allow to cool completely. Slice and serve.