Liberally grease the bottoms and sides of an eight-by-eight-inch baking pan with butter, and set it aside.

Add the three tablespoons of butter to a large saucepan over low heat. Once the butter is melted, add in the marshmallows, and stir constantly until they are melted and smooth. (This may take awhile, so it’s a good spot for a helper to step in to help stir.)

Remove the pan from the heat and stir in the potato chips. Don’t worry about whether they break and crumble as you go. Once the chips are well combined, dump the mixture into your prepared baking dish, smoothing it out evenly.

In a small, microwave-safe bowl, microwave the chocolate chips, 30 seconds at a time, until you can stir them and they are completely melted.

Drizzle the melted chocolate over top of the bars, and then top with a big pinch of coarse or flaked salt.

Let the mixture cool completely before slicing into bars. Store leftovers in an airtight container.