Pour the milk and cornflour into a pan, sieve in the cocoa powder. Add the sugar, cinnamon and orange zest, warm through while stirring.
Place the chocolate in a thin-sided bowl and suspend over a gently simmering bain-marie; the bowl must not touch the water. Melt the chocolate and stir until smooth.
Remove the cinnamon stick from the chocolate milk, stir in the chocolate, briefly bring to the boil.
Pour the hot chocolate into mugs Top with the whipped cream and chocolate sprinkles.