Line a 9x13-inch baking pan with parchment paper or non-stick foil.
In the top of a double boiler with at least 1-inch of water simmering in the bottom pan, combine the Creamy Peanut Butter (1 cup), Semi-Sweet Chocolate Chips (1 package) and Butterscotch Chips (1 package). Don’t be tempted to melt your chips in the microwave – simmering on the top of a double boiler melts the chips at a lower temperature, and easier and more consistently without the fear of the mixture seizing up.
Stir gently until melted and smooth. Remove from heat and let sit for 5 minutes, stirring occasionally.
Stir in Mini Marshmallows (1 bag) and gently stir until marshmallows are evenly coated with the melted chocolate mixture.
Pour mixture evenly into prepared baking pan – don’t press down too hard – you don’t want to squish the marshmallows!
Sprinkle with M&M's® Milk Chocolate Minis (1 cup) and refrigerate until set.
Cut into bars and serve. Store in an airtight container in a cool location.