Easy Sugar Cookie Icing

Steps

1. To make the outline icing: In a large mixing bowl, whisk together the powdered sugar, 5 tablespoons of milk, light corn syrup, and vanilla extract until well combined and no lumps remain. The mixture will be pretty thick at this point.
2. Mix in 1 additional teaspoon of milk at a time until the icing has thinned out and reached an outline consistency. To test the icing, lift the whisk or spoon from the mixing bowl; you should see ribbons of icing that fall back into the bowl for 3 to 4 seconds. If needed, add more milk to thin out the icing or more powdered sugar to make it thicker.
3. Mix in the food coloring (if using) until fully combined. Remove ⅓ of the mixture for the outline icing and set aside.
4. To make the flood icing: Add ½ to 1 teaspoon of milk at a time to the remaining two-thirds of the mixture until the icing reaches a flood consistency. When you lift your whisk or spoon from the bowl, the icing should quickly melt back into the bowl of icing.
5. To decorate your cookies: Place the outline icing and flood icing in separate piping bags, and cut a small piece of the tip off each one. Outline each cookie with the outline icing, then use the flood icing to fill in the cookie. Use a toothpick if needed to move the icing around and fill in any empty spots.
6. Place the cookies in a single layer in an airtight container, and allow the icing to harden fully for about 20 to 24 hours before stacking the cookies.