3 tbsp. butter
1 (10 oz.) bag marshmallows
6 c. rice crispies cereal
vegetable cooking spray (Pam)

Melt butter in a large pan over low heat, stirring until melted. Add marshmallows; stir often over low heat until melted completely. Take off heat and stir in cereal. Using a spoon covered with butter, press mixture into a 9 x 13 sprayed pan. Cool.