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1
Preheat oven to 275u00b0F. Bring ancho chiles and 4 cups water to a boil over medium-high. Remove from heat and let cool.
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2
Meanwhile, toast peanuts on a rimmed baking sheet, tossing once, until golden brown, 15-20 minutes. Let cool.
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3
Toast cumin seeds and peppercorns in a dry small skillet, tossing occasionally, until very fragrant, about 2 minutes. Let cool, then finely grind in spice mill or with mortar and pestle with garlic powder and cinnamon.
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4
Puree ancho chiles and soaking liquid, peanuts, spice mixture, and chocolate in a blender until smooth. Strain through a fine-mesh sieve into a Dutch oven or other large heavy pot, reserving any solids. Return solids in sieve to blender and add 3 cups water. Process until smooth and strain back into Dutch oven; discard any solids.
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5
Heat oil in a large skillet over medium-high. Season meat generously with salt. Cook, turning occasionally, until browned all over, 12-15 minutes total. Carefully add meat to Dutch oven and add bay leaves. Bring liquid to a simmer over medium-high. As soon as it just begins to bubble, lower heat, cover pan tightly with foil, then lid. Braise meat until meat shrinks off of bones and is fork-tender, 3-3 1/2 hours (check periodically to make sure liquid is at a gentle simmer).
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6
Meanwhile, puree chiles de arbol, tomatoes, broth, and oregano in a clean blender until smooth. Strain through clean sieve into a large saucepan and bring to a simmer over medium heat; cook 10 minutes to let flavors meld. Season with salt; keep sauce warm.
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7
Increase oven to 400u00b0F. Let meat cool, uncovered, in braising liquid 30 minutes. Transfer meat to a rimmed baking sheet and roast until edges begin to brown, 13-17 minutes. Pull or slice meat into servings. Divide among shallow bowls along with tomato-chile sauce.
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8
Serve meat with onion, cilantro, lime wedges, and tortillas alongside.
