Preparation Bring cream, corn syrup, sugar, cocoa, salt, and half of chocolate to a boil in a 1 to 1 1/2-quart heavy saucepan over moderate heat, stirring, until chocolate is melted. Reduce heat and cook at a low boil, stirring occasionally, 5 minutes, then remove from heat. Add butter, vanilla, and remaining chocolate and stir until smooth. Cool sauce to warm before serving. Cooks' note:Sauce can be made 1 week ahead and cooled completely, then chilled in an airtight container or jar. Reheat before using.
Preparation Bring cream, corn syrup, sugar, cocoa, salt, and half of chocolate to a boil in a 1 to 1 1/2-quart heavy saucepan over moderate heat, stirring, until chocolate is melted. Reduce heat and cook at a low boil, stirring occasionally, 5 minutes, then remove from heat. Add butter, vanilla, and remaining chocolate and stir until smooth. Cool sauce to warm before serving. Cooks' note:Sauce can be made 1 week ahead and cooled completely, then chilled in an airtight container or jar. Reheat before using.