In a medium bowl, beat the softened unsalted butter with powdered sugar using an electric mixer. Mix on medium speed for about 2-3 minutes until light and fluffy. Gradually add milk and vanilla extract until smooth.

Divide the frosting into small bowls. Add gel food coloring to each bowl and mix well until you achieve vivid colors.

Sort the Chips Ahoy cookies into pairs. Flip one cookie upside down, pipe or spread a layer of frosting on top, and then place the second cookie on top to create a sandwich.

Press candy eyes into the frosting on top of each cookie, arranging them for a whimsical effect.

Allow the cookies to set for about 30 minutes. Store in an airtight container at room temperature or in the fridge.