In a heavy saucepan, heat heavy cream and butter over medium-low heat. After the butter is melted, whisk in brown sugar.

Bring mixture to a boil and let simmer for about 5-6 minutes, whisking frequenty.

Add in vanilla slowly being carefull as the mixture will bubble. Cook an additional minute. Remove from heat and add stir in salt.

Pour the salted caramel sauce into jar or bottle and refrigerate until ready to use. To use, simply warm slightly in the microwave to loosen.