In a tall medium-sized saucepan add all the sugar to make a dry caramel.
Let the sugar melt on low heat. This can take a few minutes, let it boil until sugar turns to an amber caramel color.
Stir occasionally with a heat proof spatula if needed for even heat distribution.
When sugar is completely dissolved and turns golden brown (not dark), add a few knobs of butter & stir with a heat proof spatula.
Don’t add all the butter at once.
After all the butter is properly mixed, then slowly pour warm cream in a slow stream.
Add only 1/3 of the cream at a time and mix. Add the remaining cream until all the cream is mixed.
Allow the caramel to boil on very low heat for less than a minute, remove from heat.
Add salt and stir.
Store in a heatproof container and cover the surface with cling film. Refrigerate for up to 2 weeks.