Step 1

Get everything ready: These bars certainly aren't difficult, but once you start, it's best to keep going. If you have stop in the middle, the sauce could overcook or harden too much to stir into the cereal. First, line the baking pan with parchment and coat it evenly with nonstick spray. Then, measure the puffed rice into a large mixing bowl. Measure the sugar and corn syrup into a medium saucepan and have the peanut butter ready close by. Combine the chocolate and butterscotch chips in a heatproof bowl and set aside.

Step 2

Bring the sugar and corn syrup to a boil: Set the pan with sugar and corn syrup over medium heat. Stir to form a sandy paste, then stop stirring. Let the mixture come to a boil — as it warms, the sugar will dissolve and the mixture will become clear. Once the mixture is at a full boil with bubbles covering the whole surface, remove the pan from heat.

Step 3

Stir in the peanut butter: While the syrup is still very hot, stir in the peanut butter to form a thick, glossy sauce.

Step 4

Pour the peanut butter sauce over the puffed rice: Pour a little sauce over the puffed rice, stir it in, then pour a little more. Continue until all the sauce has been added. Continue to gently stir the puffed rice another few seconds until the cereal is evenly coated and no pockets of sauce remain.

Step 5

Transfer the cereal mixture to the baking dish: Butter your hands or spray with a little oil, and press the mixture firmly and evenly into the pan.

Step 6

Melt the chocolate chips and butterscotch chips: Melt the chips in the microwave on high for 30 seconds, then stir. Repeat until just a few tiny lumps remain. Stir until the last lumps are dissolved. (In my microwave, this took three 30-second intervals, or 1 1/2 minutes total.)

Step 7

Pour the chocolate over the cereal bars: Use a spatula to scrape every last bit of melted chocolate onto the bars. Smooth into an even layer with the back of the spatula.

Step 8

Cool until the chocolate becomes firm: Let the bars firm up for a few hours. Once the chocolate has firmed, cover the bars until ready to serve. On a hot day, you may need to put the bars in the fridge for the chocolate topping to set.

Step 9

Cut into individual bars: If your bars have been refrigerated, let them come to room temperature for a half hour or so before cutting or serving. Lift the bars out of the pan by lifting on the parchment. Use a sharp knife to cut the bars into 20 squares.

Step 10

Storing the bars: Scotcheroos will keep for at least a week or longer, and are fine served at any time. Keep the bars in an airtight container at room temperature. If it's warm and the chocolate is softening too much, you can store the bars in the fridge; just let them come to room temperature before serving or they will be brittle.