Line a half-sheet rimmed baking tray with parchment or a silicone mat.

Add the butter to a large, heavy-bottomed saucepan or stock pot. Melt the butter.

Add the marshmallows, stirring occasionally with a heat resistant spoon until completely melted.

Remove from heat. Stir in vanilla extract and green gel food coloring.

Add the cornflakes and stir until well combined, with no dry cereal remaining.

With a tablespoon, drop mixture onto prepared tray in 2-inch mounds.

Dot 3-5 cinnamon red hots on top of each mound, pressing down gently to secure.

Allow to sit, uncovered, at room temperature until cool. Layer holly leaf cookies between wax paper or sheets of parchment. Store in an airtight container at room temperature for up to 3 days.