Melt the butter and marshmallows together in a medium saucepan over low heat. Once melted, stir in the caramel sauce and remove from the heat.
Stir in the Rice Krispies until they are evenly coated with the sauce. Working quickly, stir in the peanuts and chopped Snickers bars, mixing as gently as possible.
Pour the mixture into the prepared pan and press into an even layer. Use the back of a greased wooden spoon to press down firmly over the surface of the treats to ensure that they are packed down tightly.
Melt together the chocolate chips and peanut butter in the microwave on 50% power, stirring every 30 seconds, until completely smooth and melted. Pour the chocolate/peanut butter mixture over the Rice Krispies treats and spread into an even layer with a spatula.
Refrigerate for at least 30 minutes, or until set. Cut into bars and serve. Leftovers should be stored in an airtight container at room temperature or in the refrigerator (room temperature for softer, more gooey bars; refrigerator for firmer bars).