In a medium bowl, mix 1 cup of softened unsalted butter and 4 cups of powdered sugar on medium speed for about 3-4 minutes until creamy.

Add 2 teaspoons of vanilla extract and 2-3 tablespoons of milk, mixing until fluffy for an additional 2 minutes.

Divide frosting into bowls, add food coloring, and mix to achieve vibrant Halloween colors.

Sort Chips Ahoy cookies into pairs, flipping one upside down for frostings application.

Pipe or spread frosting generously on the flat side of one cookie, placing the second cookie on top.

Press candy eyes into the frosting while it is still soft.

Let the assembled cookies sit for 10-15 minutes before serving or storing in an airtight container.