Spray bowl & pan with cooking spray

measure cereal into large bowl. in saucepan, heat 3 cups marshmallows, chocolate chips, and butter over low heat, stirring frequently until melted; remove from heat.

Pour marshmallow mix over cereal; quickly toss until completely coated, then stir in 1 cup of marshmallows.

Press mixture into an 8/9" square pan. put in fridge for 10 min, then cut into bars