Place butter in the bowl of a stand mixer with the paddle attachment.
Mix at low speed until smooth and fluffy, for about a minute.
Add the sifted powdered sugar a spoonful at a time over medium-low speed. Keep doing this until all of the sugar is added, scraping down the sides as necessary.
Add the salt and stir to combine.
Next, add in the vanilla and stir again to combine.
Lastly, add the milk and whip the frosting for 3-4 minutes until light and fluffy.
