Set out a large mixing bowl, a medium microwave-safe bowl, and a 9 x 13 inch baking dish. Line the baking dish with parchment paper. (I like to make a diagonal cut at the four corners of the paper so that it fits neatly down into the pan.)
Measure the Rice Krispies into the large mixing bowl. Then in the microwave-safe bowl, combine the peanut butter, corn syrup, and sugar. Microwave in 30-second increments, stirring in between, until the mixture is smooth.
Pour the hot peanut butter mixture over the Rice Krispies and mix until well combined. Then press the rice cereal mixture into the prepared pan, in an even layer.
Wash out the microwave safe bowl and dry it thoroughly. Then measure the butterscotch chips, chocolate chips, and butter into the bowl. Microwave in 30-second increments, stirring in between, until the mixture is very smooth.
Spread the butterscotch chocolate mixture over the top of the bars in an even layer. Sprinkle with sea salt if desired, then refrigerate, until the chocolate layer has hardened.
Lift the whole sheet of bars out of the pan by the edges of the paper, then cut into 35 regular size bars, or 70 mini bars.
