Using a coffee grinder or spice mill, grind the cacao nibs as finely as possible-this will take about 30 seconds in a standard electric spice mill.
In a bowl, combine the cacao nibs with the masa harina; add in 1 cup milk and whisk to combine; set aside.
In a 2-quart nonstick saucepan, combine the remaining 1 ½ cup milk with the honey, ground cinnamon, and salt; place over med-low heat and bring to just a boil, whisking to dissolve the honey.
Immediately whisk in the masa harina mixture; bring to a boil, then lower the heat and simmer, whisking often, for about 5 minutes, until the porridge is thick enough to hold very soft peaks with the whisk is lifted out of it.
Stir in the vanilla and remove from the heat.
Pour into 2-4 warmed cups and insert a cinnamon stick into each one to use as a spoon for the thick drink; serve immediately.