Top-ranked recipe named "Champurrado"
1. In a pot, place the hot chocolate disc in 1 cup of water and 2 cups of milk. Add the cinnamon, vanilla, brown sugar and cayenne. Heat on medium, stirring occasionally, until chocolate is melted.
2. In a blender, mix the masa harina with 1 cup of water. Add the hot chocolate to the blender, and mix with the masa until smooth.
3. Return the chocolate and masa to the pan and heat on medium low, stirring occasionally until thickened. If too thick, slowly add a bit more water until it reaches your preferred consistency.
From Homesick Texan: http://homesicktexan.blogspot.com/2008/12/cup-of-champurrado.html