For the salted caramel sauce, combine ½ cup heavy cream and 4 Tbsp butter over medium-low heat until butter is melted. Whisk in 1 cup brown sugar and bring to a boil. Reduce heat and simmer for 5-6 minutes, whisking frequently. Slowly, add 1 tsp of vanilla extract and cook for 1 minute. Remove from heat and stir in 3 tsp of kosher salt.