Line a 13x9" baking pan with foil, extending the sides of the foil over the edges of the pan. Spray the foil with cooking spray and set aside.

In a large bowl, crush the potato chips in bite-sized pieces. Just make sure they aren't teeny finely ground crumbs, but no huge pieces of chips either. If anything, err on the smaller size. Toss in 2 cups of the miniature marshmallows. Set aside.

In a large sauce pot, melt together the butter and remaining 8 cups of the marshmallows, stirring until melted and smooth. Remove from heat and whisk in the vanilla. Pour the mixture over the crushed chips. Toss to coat until moistened, and working quickly, pour the mixture into the prepared pan. Grease the bottom of a glass cup and gently compact it into the prepared pan.

Let set for about 1 hour at room temperature. Store leftovers airtight at room temperature.