Grease a 13×9-inch pan with softened butter.

In 3-quart saucepan, melt the chocolate chips, butterscotch chips, peanut butter, and butter over medium heat, stirring constantly.

Gently fold in the Rice Krispies cereal until evenly coated in the chocolate mixture.

Add the mini marshmallows and mix gently to avoid melting them completely.

Pour the mixture into the prepared baking dish, spreading it out evenly with a spatula.

Refrigerate for at least 2 hours or until firm.

Cut into squares and serve.

Store leftovers in an airtight container in the refrigerator.