In a heavy saucepan, combine the cocoa, cinnamon, cornstarch, and 2/3 cup of brown sugar. Whisk in the milk and 1/2 cup of the cream. Over medium-low heat, bring to a boil and cook, stirring constantly, until the pudding is thick and smooth. Remove from heat and stir in the vanilla.
Pour into individual ramekins or a large bowl and press plastic wrap directly onto the surface to prevent a skin from forming.
Whip the remaining heavy cream with the remaining sugar until soft peaks from. Serve the pudding warm or chilled with the raspberries and whipped cream.