Make the caramel

• Combine the sugar and water in a saucepan over medium heat without stirring.
• Cook until the mixture turns a deep amber caramel.

Add the cream and butter

• Remove from the heat and carefully whisk in the warmed cream.
• Stir in the butter until smooth.

Finish the syrup

• Whisk in the vanilla extract and salt.
• Let cool slightly, then pour into a heatproof jar and store in the fridge.