This is from the NY Times. I've tried this twice. Like most NY Times recipes it wasn't very specific. The first time I made it in a 9x13 pan but I thought they were too thick. The second time I made them in a half sheet pan with a Silpat on the bottom and they came out better. This comes out much crispier than regular Rice Krispie treats. You can use salted or unsalted butter.