In a medium saucepan, combine the sugar, water and corn syrup and bring to a boil. Using a wet pastry brush, wash down any crystals on the side of the pan. Boil over high heat until a deep amber caramel forms, about 6 minutes. Remove the saucepan from the heat and carefully whisk in the cream, butter and salt. Let the caramel cool to room temperature.
The salted caramel sauce can be refrigerated for up to 2 weeks. Rewarm before serving.