Make the base. Melt the butter over medium-low heat in a large stock pot. Add the marshmallows and stir until melted. Add the corn syrup, peanut butter, and butterscotch chips. Stir until smooth.
Add the cereal. Turn the heat to low and gently fold the cereals into the marshmallow mixture until thoroughly coated. Turn the heat off.
Form balls. Use your hands to gently form the cereal mixture into ~3-inch balls. Arrange them on the baking sheets.
Make the ganache. In a microwave-safe bowl, microwave the heavy cream until barely boiling (about 1 minute). In a separate bowl, combine the chocolate chips and hot heavy cream. Let the mixture sit for 3 minutes and then whisk until smooth.
Drizzle. Drizzle the ganache over the Scotcheroos clusters.
Notes
While these are sweet, they aren't too sweet, especially if you have a sweet tooth. However, if you like a balance of salty and sweet, you can always sprinkle these with a little bit of flaky sea salt before the chocolate drizzle dries to cut the sweetness a bit.