Heat the sugar over a medium heat. When it starts to melt whisk it. Even when it clumps up keep whisking it.
Once its all melted STOP whisking, if you need to move the sugar around the pan, swirl it around gently by the handle of the pan.
Now you have to keep your eye on the ball here, as the sugar is molten lava hot and can go from ready to burnt in the blink of an eye. It happened to me the first time!
If you are using a candy thermometer, you want it to read just bellow 350F / 120C which is setting point. We want it to remain soft and not hit setting point.
If you are doing it by eye, which is perfectly fine, just keep a close eye on the colour. You want the sugar to be a deep amber caramel in clolour, don’t allow it to get too dark.
Take it off the heat when it’s either at temperature or at the correct colour.
Add the butter and whisk it in. Once melted in add the cream slowly, and whisk it in until it is fully incorporated. This may take a little while but keep whisking and you will get there.
Then whisk in the salt.
Allow it to cool in the pan for 10 minutes.