Add the sugar to a medium sized saucepan set over medium heat. Stir occasionally until the sugar begins to melt and caramelize, then stir constantly until the sugar is completely melted, caramelized, and smooth.
Add in the butter and whisk until the mixture is smooth.
Take the mixture off of the heat, and slowly whisk in the heavy cream until it is completely incorporated into the caramel. Whisk in the salt and vanilla.
Transfer the caramel into a heat-safe container and set it in the fridge to thicken up.
Salted Caramel Frappuccino
Brew a strong batch of coffee, then place it in the fridge until it has cooled down to at least room temperature.
Add in the ice, coffee, milk, and salted caramel sauce to a blender. Blend the mixture until smooth.
Line a cup with some more salted caramel sauce, then pour the frappuccino into the cup. Top off with some whipped cream and additional salted caramel sauce if desired, then enjoy!