Warm the milk: Mix the milk, sugar, vanilla extract and spices in a medium saucepan. Gently warm over medium heat until steaming and hot all the way through.
Thicken the liquid: Add the cacao powder and cornstarch to a small bowl and add a splash of cold milk. Mix very well, then pour into the saucepan and simmer, whisking well, for 3-4 minutes or until thickened.
Melt in the chocolate: Take the pan off the heat and add the chocolate and cream. Let it melt, stir until well combined and serve hot with your favourite toppings.