1. In a bowl, cover the anchos and chipotles with the boiling water. Let soak for 30 minutes, until softened. Drain, reserving the liquid. Discard the stems, cores and seeds; coarsely chop the chiles.
2. Preheat the broiler or light a gas flame. Char the peppers for 10 minutes, turning occasionally, until charred all over. Transfer to a medium bowl, cover with plastic and let steam for 5 minutes. Peel the peppers and discard the skin, stems and seeds, then coarsely chop.
3. In a small dry skillet, toast the cloves, cumin and cinnamon stick over moderately low heat until darkened and fragrant, 1 1/2 minutes. Let cool. Grind to a powder in a spice grinder. Transfer to a plate. Add the sunflower seeds to the skillet and toast, shaking the pan a few times, about 3 minutes. Let cool. Transfer the seeds to the grinder; finely grind.
4. Heat the oil in a medium skillet. Add the garlic and cook over low heat until golden, about 3 minutes. Add the tomato paste and cook, stirring, until glossy, about 2 minutes. Remove from the heat and stir in the chocolate until melted.
5. In a blender, combine the chiles and their soaking liquid with the bell peppers, the ground spices, the ground sunflower seeds and the garlic mixture and blend until smooth. Scrape the mole into a large bowl and season with salt. Transfer the sauce to jars and refrigerate.
Make Ahead: The sauce can be refrigerated for 3 weeks.