Make this for our "English Soup" (Zuppa Inglese).
Melt chocolate with the cocoa powder in a heatproof bowl set over a pan of simmering water, stirring constantly, until thickened and difficult to stir.
Remove from heat, continuing to stir, and add sugar. Return bowl to the pan of simmering water. Heat, stirring constantly, until sugar has dissolved and sauce is smooth. Add cream; stir until smooth. Remove from heat. Let cool completely. Sauce can be refrigerated in an airtight container up to 1 day; before using, warm sauce in a bowl set over a pan of simmering water until pourable.