Using your paddle attachment in your stand mixer, cream the butter on medium speed for 2 minutes.
Turn the mixer back down to low & gradually add the sugar. Once you’ve added all of the sugar and it's fairly mixed in, turn the speed up to medium and allow the butter & sugar to cream together for about 1 minute.
Turn off the mixer & scrape the sides & bottom of the bowl with a spatula. Turn the mixer back to low & add in vanilla, cream – a little at a time, and pinch of salt. Scrape the sides of the bowl again if you need to, and then allow everything to cream together on medium speed for another minute.
Once your icing is nice and creamy, double check that you don't need to scrape the sides/bottom of the bowl anymore. If the icing is creamy & you've got an even consistency, you're ready to start decorating! (If you're not going to use your frosting right away, be sure to cover the bowl with plastic wrap to prevent a crust from forming.)
See post for LOTS of detailed decorating tips so you can make perfectly decorated cookies the first time!
Store leftover frosting in an airtight container. See notes for more details!