Whisk together the cream, cocoa powder, and sugar in a large saucepan. Heat the mixture, whisking frequently, until it comes to a full, rolling boil. Remove from heat and add raspberries. Cover and let stand for 10 minutes.
Puree the mixture in a food processor or blender. Press the pureed mixture through a fine sieve to remove seeds. Chill mixture in fridge thoroughly then freeze in your ice cream maker according to manufacturer's directions.