First, grab an 8 or 9 inch square baking pan. Spray it with cooking spray and set aside.
Place the cereal in a large mixing bowl.
Then in a medium sauce pan, heat the butter on medium until melted. Then stir in the marshmallows and butterscotch chips. Heat on medium, stirring constantly until the mixture is combined and melted.
Then pour this mixture over the cereal. You'll want to work quickly as the mixture will harden fast. Stir the cereal until the cereal is coated.
Pour the mixture to the baking pan and press the mixture into the pan. To press the mixture, I spray a piece of wax paper or parchment paper with non stick cooking spray.
Let the mixture sit for 30-60 minutes to solidify. Then slice and enjoy!
Notes
See the "How to store?" section above for storage guidance.