Pour the milk into a saucepan and add the cinnamon stick (and vanilla if using). Bring to a gentle simmer over medium heat, then remove from the heat. Cover and let it sit for 5 minutes to allow the flavours to infuse.
Remove the cinnamon stick, then whisk in the cocoa powder, chopped chocolate, sugar, and a pinch of salt. Return the pan to a low heat and whisk continuously until the chocolate has melted and the mixture is smooth and slightly thickened.
Stir in the double cream and continue to heat gently for another minute, taking care not to let it boil.
Pour into mugs and serve immediately - thick, rich, and perfectly luxurious. For an extra touch, top with softly whipped cream or a sprinkle of cocoa powder.
The video below will help with this recipe.
