Cook sugar over moderate heat in a heavy saucepan, stirring with a fork until melted and then swirling the pan until the sugar is a deep golden caramel color.
Step2
Remove the pan from the heat and add cream; the mixture will bubble up.
Step3
Simmer the mixture and stir until caramel dissolves.
Step4
Add chocolate and salt, and cook sauce over low heat, whisking until smooth.
Step5
Whisk in vanilla.
Tips & Warnings
Serve the sauce either warm or at room temperature.