Combine chow mein noodles, peanuts, and 1/2 cup butterscotch chips in a large bowl.
Combine corn syrup and peanut butter in a medium saucepan. Heat on medium heat, stirring, until melted and smooth. You do NOT need to bring the mixture to a simmer. It just needs to be warm, smooth, and easily pourable.
Pour mixture over chow mein noodle mixture. Stir to coat evenly.
Using a medium cookie scoop (2 Tbsp. size), scoop haystacks and place on parchment paper or wax paper-lined baking sheets.
Melt 1 cup of chocolate chips and 1 cup of butterscotch chips in a double boiler or microwave. I usually use my microwave and heat the chocolate chips and butterscotch chips for 30 seconds, then I stir and heat them for an additional 15-20 seconds. Every microwave is different, my advice is to go low and slow. Short intervals, stirring until smooth and creamy. DO NOT OVERHEAT CHOCOLATE.
Spoon chocolate mixture over haystacks.Allow the haystacks to stand at room temperature until the chocolate hardens or place them in the refrigerator for 20 minutes.