Line an 8×8 pan with parchment paper smeared with a little oil (doesn’t matter what kind).
Place the sugar, water, and corn syrup in a saucepan and cook over medium high heat until amber colored (approximately 10 minutes). Don’t ever stir the caramel (you risk crystallizing the caramel), just swirl it gently in the pan if you need to move it around a bit.
In the meantime, heat the cream, butter, and salt together until melted, either in a saucepan or in the microwave.
Remove the saucepan from the heat, and slowly and carefully pour in the cream mixture, being aware that the mixture will bubble up a lot (wear oven mitts if you’re concerned).
Return the pan to medium heat and cook for about 10 more minutes until it reaches 248 on a thermometer (the soft ball stage), adding the vanilla extract right before it reaches 248. Pour into the parchment lined dish and refrigerate for a few hours until hard enough to cut into squares. Enjoy!