Add all the sugar to a medium sized saucepan to make a dry caramel.
Let the sugar melt on low heat to an amber caramel color. This can take a few minutes,
Stir occasionally with a spatula if needed for even heat distribution.
When sugar is completely dissolved & golden brown (not dark), add a few knobs of butter at a time and stir with a heatproof spatula.
Pour warm heavy cream in a slow stream and mix until fully combined.
Allow the caramel to boil on low heat for a minute, remove from heat.
Add salt & stir.
Store in a heatproof container and cover the surface with cling film. Refrigerate for up to 2 weeks.