Prepare baking sheet. Prepare baking sheets or a large flat surface by lining it with parchment paper or wax paper. Add butter to a large pot and heat over medium low heat until fully melted.

Add the marshmallows. Add the marshmallows to the pot and stir until fully melted and smooth. Add the green food coloring to the melted marshmallows and stir until well combined.

Lightly grease your hands. Lightly grease your hands with a small amount of nonstick cooking spray or vegetable oil and use them to form the cornflake cookies into wreaths, creating a hole in the center.