Line a baking sheet with parchment paper or wax paper and set it beside your work area.

Add the peanut butter and butterscotch chips to a microwave-safe bowl. Microwave in 20–30-second bursts, stirring thoroughly after each burst, until smooth; alternatively, melt them together in a saucepan over low heat.

Stir the melted mixture until completely smooth, making sure it never boils. Fold in the chow mein noodles until every strand is coated, then stir in the salted peanuts if using.

Let the mixture cool for a minute or two, then gently fold in some of the candy corn or reserve it for topping. Avoid adding candy corn while the coating is very hot because it can soften or melt.

Drop heaping tablespoons of the mixture onto the prepared baking sheet, shaping each mound into a loose haystack. Work fairly quickly because the coating thickens as it cools.

Press additional candy corn or autumn-colored sprinkles onto each haystack. Refrigerate for 20–30 minutes, or until the treats are firm.