Gently heat the milk in a small pan but do not bring it to the boil.
Spoon the cocoa and a pinch of chilli (if you like things a little bit spicy) into a small jug and pour a little milk into the jug and using a small whisk, stir to make a paste. Add a little more milk and continue to stir to make sure all the cocoa is well combined. Return the cocoa mixture to the pan, and whisk in the sugar.
Heat for another minute or so, while you continue to whisk the cocoa, without boiling the milk.
Serve in cups with a cinnamon stick in each cup.