Measure your ingredients, and grab a large, heavy-bottomed pot.
Over medium heat, add the brown sugar and corn syrup, stirring fairly consistently until the sugar has fully dissolved.
Clip a candy thermometer to the side of the pan, increase the temperature slightly, and bring the mixture to a rolling boil, until the thermometer reaches the 'softball stage' (about 240℉). You can stir every now and again using a wooden spoon, but it's best to leave alone.
Once the mixture has come to temperature, remove the pot from heat and stir in the butter, heavy cream, vanilla and salt. Continue mixing until smooth and cohesive. Allow the sauce to cool before serving or storing in a glass jar with a tight-fitting lid.
Salted Caramel Sauce can be stored in the refrigerator for up to one month.