Put butter in the bowl of a stand mixer fitted with the whisk attachment.
Beat for 20 seconds, or until smooth.
Add powdered sugar and salt.
Beat on medium speed until the sugar is moist, about 45 seconds.
Scrape down the sides of the bowl with a spoon or spatula if necessary.
Beat on medium-low for another 15 seconds until the sugar is fully incorporated with the butter.
Scrape down the sides of the bowl again and add heavy cream and vanilla.
Beat until the wet ingredients are combined. Increase the speed to medium high and beat until light and fluffy (about 4 minutes).
Scrape down the bowl a few times during that process to make sure you aren't ignoring any frosting.