In large
bowl, stir together sugar and cocoa. Add egg yolks and blend with
electric mixer. Add cream a little at a time, beating well after each
addition. Chill mixture in refrigerator.
While cream
mixture is chilling, grate chocolate chips in blender or food processor
or using a rotary grater, until fine. Stir into cream mixture. Freeze in
canister of ice cream maker according to manufacturer's instructions.