One of Oaxaca's rarest moles, made with burned chile seeds for a distinctive ashy, complex flavor. This dark, intense family celebration sauce represents the pinnacle of Oaxacan mole artistry.
Place beef shank in a large pot with 10 cups water. Bring to a boil, skim off foam, then lower to a gentle simmer; cook for 1 hour, covered, until the beef is just tender.
While beef simmers, toast the seeds of all chiles in a dry skillet over medium-high heat, stirring constantly, until deeply blackened but not fully burned—about 5 minutes. Remove immediately to prevent acrid flavors.
Roast chiles lightly in the same skillet until fragrant, about 1 minute per side; soak in hot water until pliable, then blend with tomatoes, onion, and garlic to a smooth paste.
Heat lard in a large Dutch oven over medium heat. Fry the chile paste, stirring constantly, for 10 minutes until it darkens and thickens, being careful not to scorch.
Grind the burned seeds, cloves, cumin, peppercorns, oregano, and cinnamon into a fine powder. Add this spice mix and the masa, and combine well with the fried paste.
Add the beef broth (from step 1), beef pieces, salt, and vegetables. Simmer gently on low heat—covered—for 90 minutes, stirring occasionally to avoid sticking.
Finish with final seasoning to taste, and allow to rest for 15 minutes before serving so flavors blend and sauce thickens properly.