In a medium saucepan, preferably with a light-colored interior, add the sugar and heat it over medium heat. You want to stir this occasionally as the sugar melts in the pan, and it will clump up through the process. It takes about 6-10 minutes for the sugar to completely melt and turn a deep amber color. There should be no remaining clumps of sugar.

Whisk in the butter one tablespoon at a time. The mixture will bubble and sizzle up when you add the butter, just keep whisking until all the butter has been added and stirred through completely. Remove from the heat and slowly whisk in the heavy cream. When you add the heavy cream, it will bubble up violently, so be careful during this step! Continue to whisk until the cream is well incorporated.

If your mixture seizes up at this stage and you have clumps or big globs of caramel instead of a smooth sauce, place the pan back over medium heat, whisking constantly, for about 2-3 minutes, or until the caramel sauce smooths completely.

Finally, whisk in the salt and vanilla extract or paste until smooth, and pour the sauce into a heat-proof jar to cool completely before enjoying!