My original recipe used an 8x8" pan, but let's face it: more is better! Go ahead and use a 9x13" pan; you'll thank me for it, even if your waistline doesn't. And, as with most marshmallowy desserts, they actually get better after sitting for a few hours. I would even go so far as to say let them sit overnight. I know, I know. Good luck with that one!