[header] How to make rice krispie monster treats [title] Prepare a 9 x 13-inch baking pan. [step] You can choose to grease the pan by spraying non-stick cooking spray all over it, or you can cover the pan with parchment paper. [title] Melt the butter in a medium-sized pan over lower heat. 
[step] Stir gently with a rubber spatula until fully melted. [title] Fold in the marshmallows and mix once more until the marshmallows melt.