In a large bowl with an electric mixer or the bowl of a stand mixer fitted with a paddle attachment, beat the butter and salt on medium-high speed for 5 minutes or until pale, smooth and creamy. Scrape down the bowl halfway through.
Reduce the mixer to low, and add the powdered sugar a ½ cup at a time. Add 2 to 3 tablespoons of cream intermittently as you are mixing in the sugar. Stop occasionally to scrape down the bowl and make sure all of the sugar is getting mixed in. Add in the vanilla extract.
Once all of the sugar is added, mix on medium-low for 1 minute until light and fluffy. If desired, add the additional cream 1 teaspoon at a time until the frosting is smooth and easily spreadable or thick enough for piping your decorations.