Add 10 cups water, cinnamon sticks, cloves, and allspice berries to a large pot and bring to a boil. (You can add your sugar at this point as well, if you choose to use it; the chocolate discs are already sweetened.) Once the water has taken on the color of tea from the spices, reduce to a simmer and add chocolate discs. Once the chocolate has dissolved, add milk and return to a simmer.
While the pot of champurrado is coming back to a simmer, take your masa harina or tortilla masa and add to a blender with two cups of cold water. Blend until smooth; then add slurry to the pot of champurrado through a fine mesh strainer to avoid any clumps, stirring continuously.
Bring everything back to a boil then reduce to a simmer. Allow to simmer for about 10 minutes while the mixture thickens. At this point you can add more milk or more of the masa slurry depending on how thick or thin you prefer. You can also add more chocolate if you'd like. The final product should coat the back of a spoon, not be too sweet and should have the flavor of chocolate, cinnamon and corn. Garnish with shaved chocolate, an orange peel, or a whole dried chile de arbol (careful not to eat it!)