Step 1: Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
Step 2: In a large saucepan, combine the granulated sugar and corn syrup. Cook over medium heat, stirring constantly, until the mixture comes to a full, rolling boil. Remove immediately from heat.
Step 3: Stir in the creamy peanut butter until it is completely melted and smoothly incorporated into the sugar mixture.
Step 4: Add the crispy rice cereal to the peanut butter mixture. Gently fold it in with a rubber spatula until all the cereal is evenly coated.
Step 5: Transfer the cereal mixture to the prepared pan. Using another piece of parchment paper or a lightly greased spatula, firmly and evenly press the mixture into the pan.
Step 6: In a microwave-safe bowl or over a double boiler, combine the butterscotch chips and chocolate chips. Melt in 30-second intervals in the microwave, stirring after each, until smooth and fully melted.
Step 7: Pour the melted butterscotch and chocolate mixture evenly over the pressed cereal base. Use an offset spatula or the back of a spoon to spread it from edge to edge.
Step 8: Place the pan in the refrigerator for at least 1 hour, or until the topping is completely set. Once firm, use the parchment paper overhang to lift the slab out of the pan. Cut into squares or bars with a sharp, warm knife before serving.