In a medium saucepan, combine sugar and water. Heat over medium-low, stirring until the sugar dissolves.
Increase heat to medium-high and bring to a boil without stirring. Watch closely until the mixture turns a deep amber color, about 5-7 minutes.
Remove from heat and carefully whisk in the heavy cream. The mixture will bubble vigorously.
Stir in butter, vanilla extract, and a pinch of salt until smooth.
Allow the syrup to cool completely before transferring to a jar or bottle for storage.
Notes
Keep stirring the sugar and water on low heat until the sugar dissolves completely.
• Watch the caramel closely as it can burn quickly once it starts to change color.
• Remove from heat before adding cream to prevent splattering.
• Stir in butter and vanilla extract off the heat for a smooth consistency.
• Let the syrup cool completely before using or storing.