Cream the butter – Place softened butter in a bowl and beat until pale, fluffy, and smooth. [The butter should turn almost white]
Add the sugar – Sift icing sugar into the bowl, half at a time, mixing on low speed until fully incorporated.
Flavor – Stir in vanilla extract and continue beating until light and airy.
Adjust consistency – If the frosting is too stiff, add 1 tsp milk at a time; if too soft, add a little more icing sugar.