In a large mixing bowl, beat the softened unsalted butter with an electric mixer on medium speed until light and fluffy for 2-3 minutes.

With the mixer on low speed, gradually add the sifted powdered sugar, one cup at a time, until fully incorporated.

Pour in the vanilla extract, a pinch of salt (if using), and slowly add 2 tablespoons of milk, a little at a time, mixing until combined.

Increase the mixer speed to medium-high and beat for another 2-3 minutes until the frosting is smooth and creamy. If too thick, add milk 1 teaspoon at a time until desired consistency.

If using food coloring, divide frosting into separate bowls, add a tiny amount of gel food coloring to each, and mix until the desired shade is achieved.

Transfer frosting to piping bags or use an offset spatula for spreading, then decorate cooled sugar cookies.