Have ready a large sheet of wax paper set across your workspace.
Add the butterscotch chips and peanut butter to a microwave-safe bowl or measuring pitcher and microwave at 50% power for 1 minute. Stir and continue to microwave at 30-second intervals, stirring after each interval until the chips are melted. Add the salt and stir until smooth.
Add the chow mein noodles and miniature marshmallows and fold them into the peanut butter-butterscotch mixture until completely coated.
Spoon out generous heaping spoonfuls of the mixture (about 2 tablespoons worth), and set on the wax paper. Sprinkle each cookie with a pinch of nonpareils and allow to sit at room temperature for at least 4 hours, or refrigerate until firm (see note below).
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Notes
If you would like for your haystack cookies to set faster, you'll want to refrigerate them. Rather than placing wax paper directly on the counter, place it on a baking sheet so it can be easily transferred to the refrigerator.