Prepare 13x9 pan by greasing with butter, or spraying with oil. Set aside.

Add butter to large pot. Begin to melt the butter over a medium heat. When butter is about 80% melted, add the marshmallows. Stir to melt marshmallows into the butter. Once completely melted, add half of the cereal, and stir. Add the balance of cereal, and continue to stir to completely mix.

Add cereal mixture to greased pan, and press down with a buttered spatula. Allow to cool for at least 30 minutes. May cool longer.

Lay a sheet of parchment over the top of the Lucky Charms treats. Then put a cutting board over the parchment and flip pan over. Once the Lucky Charms treats come out of the pan, slice into 24 pieces.

Store the Lucky Charm treats in a sealed container. Will stay fresh for about a week.