Place the softened unsalted butter in the bowl of a stand mixer fitted with the whisk attachment. Beat on medium-high speed until the butter becomes light and fluffy, which should take about 3 minutes. Scrape down the sides of the bowl as needed to ensure even mixing.

Add the vanilla extract to the whipped butter and mix on medium speed until well combined. This helps infuse the butter with a rich vanilla flavor, which I think makes the frosting extra special.

With the mixer on low speed, gradually add the sifted powdered sugar, whole milk, and a pinch of kosher salt to the butter mixture. Frequently stop to scrape down the sides and bottom of the bowl to ensure everything mixes evenly. Continue mixing on low until all ingredients are just incorporated.

Increase the mixer speed to medium-high or high and whip the frosting for at least 3 minutes, or up to 7 minutes for an extra fluffy and smooth consistency. I like to let my mixer run a little longer to get the frosting ultra light.

If the frosting is too thick to spread, slowly beat in additional milk (up to 1/2 cup as needed) until your desired consistency is reached. Be sure to add the milk a tablespoon at a time to avoid making the frosting too runny.