Line a 9x13-inch baking pan with parchment paper, leaving some overhang on the sides to make it easier to lift the bars out later. Set aside.
Place a large saucepan over low-medium heat and add the granulated sugar and corn syrup. Stir continuously until the sugar has completely dissolved and the mixture is hot. Do not allow it to come to a boil, as this can make the bars hard once cooled (see note 1).
Remove the saucepan from the heat and add the peanut butter and vanilla. Stir until smooth and fully combined.
Add the crispy rice cereal and gently fold until all of the cereal is evenly coated in the peanut butter mixture.
Transfer the mixture to the prepared baking dish and spread it out evenly. Using a piece of parchment paper as a barrier, gently press the mixture into place. Avoid pressing too firmly, as this can make the bars dense and hard once set (see note 2). Set aside.
In a microwave-safe bowl, combine the chocolate chips and butterscotch chips. Microwave in 20-second intervals, stirring well between each interval, until fully melted and smooth. Be careful not to overheat the chocolate.
Pour the melted chocolate mixture over the cereal layer and spread it evenly to the edges using an offset spatula or the back of a spoon. Shake the pan if needed to smooth the surface.
Allow the Scotcheroos to cool completely at room temperature until the topping is fully set.
When ready, run a sharp knife around any edges not lined with parchment paper. Use the parchment overhang to lift the Scotcheroos out of the pan, then slice into squares and serve.