Heat a heavy skillet over high heat; add the pumpkin seeds, and
dry-roast until the seeds start to pop. Shake the skillet once they
start to pop, continuing until they turn golden, about 3 to 5 minutes. Take care that they don’t darken and remove from the pan to cool completely.
Place the seeds in a spice mill or coffee grinder and process to a fine powder.
Put the pumpkin seeds, tomatillos, tomato, chile seeds, tortilla, chile powder, and annatto or achiote in a blender or food processor and process, using just enough broth to form a paste.
Reheat the skillet over medium heat, add the oil, and when hot, add the paste. Fry the paste, stirring constantly, until fragrant, about 4 minutes.
Whisk in the remaining chicken broth and the chocolate, and cook,
stirring constantly, until thickened to desired consistency. If the
sauce becomes too thick, thin with either broth or water.