Put honey, cocoa powder, water and salt in a medium saucepan. If doubling this recipe, use a larger stock pot as it tends to foam up and expand before boiling.
Cook over medium heat, whisking to remove lumps and to keep from burning. Bring to a boil so it will thicken for 2-3 minutes, all the while whisking to avoid burning.
Remove from heat and allow to cool for 5-10 minutes before adding the vanilla.
Add vanilla and cinnamon if you so choose.
This will store in a fridge for up to 4 weeks... it probably won't last that long before disappearing though.
My kids like their chocolate milk strong. For an 8 ounce glass we add 2-3 tablespoons of syrup.