8cupswhich is most of 453g box Lucky Charms cereal, divided
Place sprinkles in a shallow dish. Dip the ice cream cones in the melted chocolate to coat the top edge. Immediately dip cones into rainbow sprinkles. Stand cones upright in small tumblers or coffee mugs. Allow to dry.
In a microwave or a large saucepan over low heat, melt the marshmallows and butter. Stir until smooth. Stir in 6 cups of the cereal and remove from heat. Mix well so that all the cereal pieces are coated with the marshmallow mixture. Let mixture cool slightly. Spoon 2 tablespoons of the cereal mixture into the bottoms of each cone.
Have a small bowl of cool water ready to hand. Working quickly, dip hands in water and shape mixture into 8-10 balls. Pack firmly on top of the cones. Let stand upright in small tumblers until set.
Place the remaining 2 cups of cereal into a medium bowl. Dip the tops of the cones into the cereal, pressing the pieces onto the top of the cone with your hands.
Store cones airtight, or package individually in cellophane bags tied with ribbon.
Alternate prep: Omit the cones and press the treat mixture into a 13×9 dish. Press dry cereal on top (you may not need the entire 2 cups). Let set and cut into bars.