Add the sugar to a medium sized saucepan. Turn on the heat to a medium setting and stir intermittently to avoid the sugar burning.
2 Cups Light Brown Sugar
Keep stirring, until the sugar has liquified. Continue to cook and stir. Once the sugar has turned a dark brown (almost black) turn off the heat, but keep stirring.
Slowly pour in the boiling water, while still stirring.
1 Cup Boiling Water
Add the salt and allow to cool before decanting to a jar with a lid.
1 teaspoon Salt
Notes
Once the sugar has liquified, don't stop stirring at this point. The sugar can quickly foam up and overflow your pan. Don't use a pot that is too small to help avoid this.