Boil sugar, water, corn syrup, and salt in a saucepan over medium-high heat, swirling occasionally.
Cook until caramel is the color of iced tea, about 10 minutes. Watch it closely. It takes about 10 minutes to get going, but once it does, it can scorch quickly.
Remove from heat and add cream and bourbon (watch out for steam!), whisking quickly to combine. Once the cream is mixed whisk in butter and vanilla.
Transfer sauce to a bowl to cool (and thicken). Store covered in the fridge and reheat slowly in the microwave or over low heat in a saucepan.
Super yummy with apples as a dip.