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