In a saucepan, whisk together cocoa powder, sugar, salt, cayenne powder, cinnamon and 1/4 cup of milk until they are well combined.
Add remaining milk and bring to a boil, whisking well all the while.
Remove from flame, stir in the tequila.
In a flat dish, spread the powdered sugar with a pinch of salt. Rub the rim of the glass with some water and then place the rim on the sugar-salt mix to get a frosting effects around the entire rim. You can keep this rustic looking, so don't aim for perfection :)
Pour the hot chocolate into both the prepared glasses. Dust with some cocoa powder in a sieve. Garnish with a stick of cinnamon. Serve warm/hot.