Place the sifted powdered sugar into a medium mixing bowl to ensure a smooth, lump-free frosting base.
Add the room temperature butter to the powdered sugar. Use a whisk or hand mixer on low speed to start blending until the mixture is crumbly and begins to come together.
Increase the mixer speed to medium and beat for 1-2 minutes until the mixture turns pale, fluffy, and fragrant with vanilla aroma.
Pour in the vanilla extract and mix briefly to incorporate it evenly into the frosting.
Gradually add the milk, starting with about a teaspoon, and continue mixing on low until the frosting reaches a smooth, creamy consistency that holds stiff peaks but spreads easily.
If the frosting is too thick, add a tiny splash more milk; if too runny, sprinkle in a bit more sifted powdered sugar and mix again until perfect.
If desired, mix in gel food coloring to achieve vibrant shades before piping or spreading onto cookies.
Transfer the frosting into a piping bag fitted with your favorite tip or use a spatula to spread it smoothly over cooled cookies.
Pipe or spread the frosting onto cookies, creating decorative shapes or elegant borders. Let the decorated cookies sit at room temperature for 10-15 minutes to allow the frosting to set with a glossy, velvety finish.
Enjoy your beautifully frosted cookies, which should feel light, silky, and melt-in-your-mouth with every bite.
