Line a 13×9 pan with foil or parchment paper and lightly grease with butter. Set aside.

In a large pot, combine corn syrup, sugar, and butter over medium-low heat, stirring occasionally until butter is melted and ingredients are well-combined.

Increase heat to medium-high and stir frequently. Once mixture just begins to boil (as soon as it starts bubbling) remove from heat and stir in peanut butter, vanilla extract, and salt.

Stir well until mixture is smooth.

Stir in cereal — make sure ingredients are well-combined.

Spread ingredients evenly into prepared pan. If you're having trouble spreading the cereal, place a piece of wax paper overtop and use your hands (careful, it's hot) or the back of a spoon to smoothly press into pan. Set aside while you prepare your chocolate topping.

In a medium-sized microwave safe bowl, combine semisweet chocolate chips, 1 cup (170g) butterscotch chips, and 1 teaspoon coconut oil or vegetable shortening, if using (this helps the chocolate spread more smoothly).

Microwave for 30 seconds, stir well, and return to microwave at 15-second increments, stirring well in between until mixture is completely melted and smooth. Set aside.

Immediately melt remaining ¼ cup (56g) butterscotch chips and ½ teaspoon coconut oil or vegetable shortening (heat in 15 second increments, stirring between).

Spread melted chocolate/butterscotch evenly over prepared scotcharoos. Drizzle melted butterscotch chips over the chocolate and then drag a toothpick through the chocolate to create swirls.

Allow chocolate to set (about an hour at room temperature) before cutting and serving.