Preheat the oven to 300ºF. Lay a kitchen towel along the bottom of a large roasting pan. Place six 4-5 ounce ramekins on top of the towel; set aside.
Pour the heavy cream into a medium saucepan and cook over medium heat until it starts to simmer. Remove from heat; set aside.
In a large bowl, whisk the egg yolks, sugar, and vanilla together until thick, pale, and forms a nice ribbon when you lift the whisk from the bowl. Gradually add the salted caramel, whisking constantly as you pour.
Gradually add the warm cream by whisking in about a half cup. Whisk in another half cup, then finally pour the rest of the cream in, stirring until smooth. Pour mixture through a fine mesh sieve to remove any lumps that might have formed.
Divide custard evenly among the six ramekins, then set the pan on the oven rack. Carefully pour enough hot water into the pan to come about halfway up the sides of the ramekins. Bake for 40-50 minutes, or until the edges are set, and the centers jiggle when you gently shake the pan. You can also use a food thermometer to take the internal temperature. It should be 170ºF/77ºC.
Transfer ramekins to a wire rack and allow to cool to room temperature, about 2 hours. Place ramekins on a baking sheet, cover tightly with plastic wrap, and refrigerate for at least 4 hours or overnight.
Just before serving, sprinkle about 1 teaspoon of granulated sugar evenly over each custard.** Use a small kitchen torch to caramelize the tops.
Drizzle with remaining caramel. Add a dollop of whipped cream, if desired. Enjoy!