Place the crisp chow mein noodles and salted peanuts in a large mixing bowl. Gently toss them together until the peanuts are evenly dispersed throughout the noodles, then set the bowl aside.
Add the butterscotch chips and creamy peanut butter to a separate heat-safe bowl. Melt the two ingredients together in the microwave or over a double boiler, using gentle heat only until fully melted. Avoid overheating the mixture.
Whisk the melted butterscotch and peanut butter until the mixture becomes smooth and evenly blended. Pour it over the prepared noodles and peanuts.
Using a silicone spatula, carefully fold and stir the ingredients until the chow mein noodles and peanuts are uniformly coated. Work gently so the noodles remain as intact as possible.
Line a baking tray with parchment paper or wax paper. Portion the mixture onto the prepared tray using a 2-tablespoon scoop. If using an ice cream scoop, handle the mixture carefully to prevent crushing the noodles. Two spoons—one larger and one smaller—may also be used to form the characteristic haystack shape.
Immediately scatter optional festive sprinkles over each cookie cluster before the coating begins to firm.
Leave the cookies undisturbed at room temperature for approximately 3–6 hours, or refrigerate them for about 1 hour, until completely firm and set.
Once fully hardened, serve the Christmas noodle cookies.