Begin by placing the butterscotch chips and creamy peanut butter in a microwave-safe bowl.
Microwave the mixture for 30 seconds, then remove and stir. Repeat this process in 15-30 second increments until the mixture is silky smooth and completely melted, which should take around 1 to 1.5 minutes in total.
Once melted, stir in the vanilla extract and a pinch of salt until fully combined.
In a large mixing bowl, combine the Chinese chow mein noodles, mini marshmallows, and shredded coconut (if you're using it). Mix them gently to avoid crushing the marshmallows.
Carefully pour the melted butterscotch and peanut butter mixture over the noodle mixture. Using a spatula or your hands, gently fold the ingredients together until all of the dry components are thoroughly coated.
With a spoon or a cookie scoop, drop generous spoonfuls of the mixture onto a baking sheet lined with parchment paper.
Allow the haystacks to cool at room temperature until they are firm, or refrigerate them for about 30 minutes to help them set more rapidly.
Once the cookies are set and firm to the touch, they are ready to be enjoyed!
Notes
For a fun touch, consider drizzling melted chocolate over the cooled haystacks or serving them in colorful cupcake liners.