Combine whipping cream and sugar in a heavy saucepan. Place over medium heat, and cook, stirring constantly, until sugar dissolves. Stir in chocolate, corn syrup, and butter. Cook over medium-low heat, stirring occasionally, until chocolate melts and all ingredients are blended. Remove from heat; stir in vanilla and salt. Let cool to room temperature. Transfer sauce to jars with tight-fitting lids. Store in refrigerator. To serve, spoon sauce into a microwave-safe bowl, and microwave at HIGH for 20-second intervals or until pourable.