In a stand mixer fitted with a paddle attachment, cream the butter. Start off at a low speed and then gradually increase until the butter is light in color and
smooth. Use a rubber spatula to scrape the bowl as needed.
Add the sugar, one cup at a time, mixing at a low speed until fully incorporated before you add the next cup.
Add the caramel sauce, vanilla and salt and beat at a low speed for
about 20 seconds. Increase the speed to high and beat for about 5 minutes until
the mixture is perfectly smooth and creamy. Stop the mixer a couple times to
scrape the bowl.