Heat the white sugar on a pot over medium heat, stirring constantly. Sugar will first form clumps and then melt into a thick brown liquid.
Once the sugar is completely melted, add the butter and keep stirring constantly. If butter and sugar are not properly mixed, remove from the heat and whisk it energetically until combined.
Cook for one minute without stirring.
Add the cream very slowly and whisk energetically. The caramel will bubble as the cream is much colder. When all the cream is added, stop stirring and let it boil for 1 minute.