Mix sugar, corn syrup, and 1/2 the cream in a large heavy-bottomed sauce pan.

Over medium heat, bring the mixture to a boil.

Boil 10 minutes.

Slowly add the rest of the cream.

Boil 5 minutes.

Add the butter bit by bit while you are stirring.

Cook until the temperature reaches 244°F, remove from heat and add vanilla and salt.