How to Make It
In a medium saucepan, bring the cream and sugar to a boil over moderately high heat. Reduce the heat to low and simmer, stirring occasionally, until the liquid reduces slightly, about 6 minutes. Pour the mixture into a medium bowl and add the chocolate, butter, vanilla and salt. Let stand, stirring occasionally, until the chocolate and butter are melted.
Set the bowl in a larger bowl of ice water. Using a hand-held electric mixer, beat the frosting on medium speed, scraping the sides occasionally with a rubber spatula, until thick and glossy, about 5 minutes. Use at once.