In a bowl, whisk together the masa harina with 1 cup of milk.
In a large dutch oven, whisk together the remaining 7 cups of milk, pumpkin puree, brown sugar, vanilla extract, and the nutmeg. Add in the cinnamon sticks then bring to a simmer over medium heat, about 8-10 minutes.
Whisk in the masa harina slurry, then reduce the heat to medium -low and cook until it starts to thicken, 10 to 12 minutes. Stir often to prevent the milk from burning.