01 - Heat sugar in a medium heavy-bottomed saucepan over medium heat. Stir constantly with heat-resistant spatula or wooden spoon as sugar melts, clumps together, then transforms into golden-brown liquid.
02 - Once sugar completely melts and caramel reaches deep amber color, carefully add butter cubes. Mixture will bubble vigorously—keep stirring until butter fully melts and incorporates.
03 - Slowly pour heavy cream while stirring. Mixture will bubble up again; continue stirring until smooth and fully combined.
04 - Remove from heat. Stir in salt and vanilla extract.
05 - Allow sauce to cool for 10–15 minutes before using. Caramel will thicken as it cools.