In a mixing bowl with a paddle attachment, whip butter on medium high speed for about 2 minutes, or until pale and fluffy. Scrape the sides and bottom of the bowl with a silicone spatula half way through. TIP: Incorporating as much air into the butter before adding sugar and flavorings ensures light and fluffy frosting. If the butter is not whipped well, the frosting will be heavy, kind of greasy and won't hold its shape well.
Add half of the powdered sugar and mix on low speed until sugar is incorporated.
Then add the reamining powdered sugar, vanilla extract, and salt. Start on low speed and then gradually increase it to medium high and continue beating until the frosting is nice and smooth and fluffy, about 2 more minutes.
Yield: This recipe makes enough frosting for 18 cupcakes (moderately frosted).Make-Ahead Tip: Store the frosting in an airtight container in refrigerator for up to 1 week, or in freeze for up to 3 months. Thaw the frozen frosting in the fridge overnight. Bring the frosting to room temperature and whip it again in the mixer until fluffy.