Blend masa. Combine water and masa harina in a blender and blend on high until smooth.

Bring to a simmer. Pour masa mixture into a large 4-quart saucepan. Add milk, piloncillo, and chocolate and place over medium heat. Bring to a simmer, whisking constantly with a molinillo or wire whisk until chocolate is melted and piloncillo is dissolved.

Serve. Strain through a fine mesh sieve if you'd like it super smooth and serve hot.