Rub together the flour, salt and butter with your fingers until it is nice and crumbly
Pour the milk into a large saucepan and add the cinnamon stick. Bring to the boil. Once the milk is boiling and frothy, reduce the heat and allow to simmer while slowly sprinkling the crumbs into the milk, whisking.
Reduce the heat and simmer gently, while whisking continually, for about 10 minutes. Turn off the heat, allow to rest for 5 minutes before serving with a generous sprinkling of cinnamon sugar