Place your sugar thermometer into a medium, heavy saucepan
Add the sugar, corn syrup and ½ cup of the cream
Bring to a boil and boil for 15 minutes.
Add the remaining cream and the butter, gently stir to mix in the melting butter. The mixture should be a rich golden colour now.
Boil until it reaches 248c (in between soft and hard ball stage)
Remove from the heat and stir in the vanilla extract.
Now pour into your prepared dish and leave to cool completely for at least 3 hours.
Sprinkle with Sea Salt if using.
Once cold, turn out onto chopping board and cut into squares of your liking. Wrap in the caramel wrappers.