Slit the vanilla bean lengthwise and heat in a pan with the milk and the sugar.
Break both chocolates into small pieces and set aside a little of each for garnish. Stir both chocolates into the vanilla milk and allow to melt. Remove from the heat and remove the vanilla pod. Pour the hot chocolate into cups and garnish each with a swirl of whipped cream. Sprinkle with cocoa and serve with small chocolate pieces.