Line 2 baking sheets with parchment paper or silicone baking mats. If your kitchen is warm, clear space in the refrigerator so the sheets can chill later.

In a large mixing bowl, add the crispy chow mein noodles and shredded coconut. Gently toss them together with your hands or a large spoon until evenly mixed.

In a medium microwave-safe bowl, combine the semi-sweet chocolate chips, butterscotch chips, peanut butter, and coconut oil or butter. Microwave on 50% power for 30 seconds, then stir well. Continue heating in 20–30 second bursts at 50% power, stirring thoroughly after each interval, until the mixture is fully melted, smooth, and glossy. Stovetop option: Place the ingredients in a heatproof bowl set over a saucepan of barely simmering water (double boiler). Heat, stirring often, until completely melted and smooth.

Remove the melted mixture from the heat and stir in the vanilla extract and fine sea salt. Taste a tiny amount carefully and adjust the salt if needed.

Pour the warm chocolate-peanut butter mixture over the chow mein noodles and coconut in the large bowl. Using a large spatula or wooden spoon, gently fold the mixture together until all of the noodles and coconut are mostly coated. Avoid crushing the noodles; stop mixing once only a few small uncoated spots remain.

Using a tablespoon, small cookie scoop, or two teaspoons, drop 1 1/2–2 tablespoon mounds of the mixture onto the prepared baking sheets. If any noodles stick out excessively, gently nudge them back into the mound. Aim for even-sized haystacks so they set at the same rate.

While the haystacks are still soft, sprinkle them with flaky sea salt, festive sprinkles, and/or chopped roasted peanuts, if using.

Place the baking sheets in the refrigerator for 20–30 minutes, or until the haystack cookies are firm to the touch. Once set, transfer them to an airtight container. Store at room temperature if your kitchen is cool, or keep refrigerated in warm or humid conditions.