To make in a food processor, grind the chocolate to crumbs and then, with the motor running, add the simmering cream mixture. By the time the last of the cream has been added, the chocolate will be melted and the sauce will be smooth.
Combine in a medium heavy saucepan:
Bring to a rolling boil, stirring constantly. Remove from the heat and immediately add:
Let stand for 1 minute, then whisk until smooth. Whisk in:
Serve warm or cold; the sauce will thicken as it cools and take on the consistency of ganache after a day in the fridge. Cover and refrigerate for up to 2 weeks. Reheat over low heat, whisking in a little hot water if the sauce looks oily.