01 - Heat 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 all sugar has melted and caramel reaches a deep amber color, carefully add butter cubes. The mixture will bubble vigorously; keep stirring until butter is completely melted and incorporated.
03 - Slowly pour in heavy cream while stirring continuously. The mixture will bubble up again; continue stirring until sauce becomes smooth and fully combined.
04 - Remove from heat. Stir in salt and vanilla extract until well incorporated.
05 - Allow sauce to cool for 10–15 minutes before using. The caramel will thicken considerably as it reaches room temperature.