Sifting the Powdered Sugar: Begin by sifting the powdered sugar into a medium to large bowl to ensure a fine, lump-free texture.
Combining Ingredients: To the sifted sugar, add the corn syrup, vanilla extract, and milk or water. Stir the mixture vigorously to ensure a smooth and homogenous consistency.
Adjusting Consistency: If the mixture appears overly thick, incrementally add additional milk or water. The desired consistency should be such that the icing slowly drips off the spoon, leaving a substantial layer.
Preparing Multiple Colors: Should you require multiple colors for decoration, divide the icing into separate smaller bowls. Add gel food coloring to each as per the desired shade.
Decoration and Setting: Use the prepared icing to decorate cookies. Post-decoration, allow the icing to set at room temperature. This step is crucial for the icing to harden appropriately before storage.