1-Pour the milk into a saucepan and: 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 flavors to infuse.
2-Remove the cinnamon stick, then whisk in: Remove the cinnamon stick, then whisk in the cocoa powder, chopped chocolate, sugar, and a pinch of salt. Return the pan to low heat and whisk continuously until the chocolate has melted and the mixture is smooth and slightly thickened. This will take 5-10 minutes.
3-Stir in the heavy (double) cream and: Stir in the heavy (double) cream and continue to heat gently for another minute, taking care not to let it boil.
4-Pour into mugs and serve immediately –: Pour into mugs and serve immediately – thick, rich, and perfectly luxurious. For an extra touch, top with softly whipped cream, marshmallows, or a sprinkle of cocoa powder. My Easy Homemade Marshmallows would be incredible here!