Oven-Braised Lamb Barbacoa

Toast and soak the guajillos. Set an oven rack to the lower-middle position and heat the oven to 160 °C (140 °C fan). Toast the guajillo chiles in the skillet over medium-high heat, stirring often, until fragrant, 2-6 minutes. Tip into a bowl, pour over the hot water so the chiles are completely submerged, and leave to soften for about 20 minutes.

Trim and portion the lamb. Lay the lamb fat side down and trim away any pockets of fat or connective tissue from the underside. If any part is thicker than 3.8 cm, cover with plastic wrap and pound it down (it doesn't need to be an even shape, just no part much thicker than the rest). Cut the lamb crosswise into 3 pieces and put it in a large bowl.

Blend the marinade and coat the lamb. Drain the guajillos, reserving 160 ml of the soaking liquid and discarding the rest. Blend the chiles with the reserved liquid, 4 of the garlic cloves, 2¼ tsp of the fine salt, the oregano, cider vinegar, pepper, whole cloves and cumin until smooth, about 3 minutes. Pour the paste over the lamb and toss with tongs until every piece is coated.

Build the braising pot. Stand the ramekin upright in the centre of the Dutch oven. Working around it, add the braising water, chickpeas with their liquid, potatoes, onion half, carrots, bay leaves, the remaining 2 garlic cloves and the remaining ¼ tsp fine salt. Set the plate on top of the ramekin to make a stand.

Braise the lamb. Arrange the lamb on the plate, two pieces side by side with the third on top, and scrape any marinade left in the bowl over the meat. Bring to a simmer over high heat, cover tightly, and transfer to the oven. Cook until a paring knife slides into the lamb with almost no resistance, about 3 hours. Leave the meat to rest, covered, for 30 minutes.

Char the vegetables for the salsa. While the lamb cooks, toast the ancho chiles in the same skillet until fragrant, 2-6 minutes, then soften in the hot water for about 20 minutes, same as the guajillos. In the empty skillet over medium-low heat, char the tomatillos, tomato, quartered onion and unpeeled garlic, turning occasionally: the garlic until the skins are lightly charred and the inside is soft, about 5 minutes; the onion until both cut sides are lightly charred and slightly softened, 12-15 minutes; the tomatillos and tomato until the skins are spotty brown and the flesh is soft, 20-25 minutes.

Blend the salsa. Peel the charred garlic and trim the root end from the onion. Drain the anchos, reserving 160 ml of their soaking liquid. Blend the garlic, onion, tomatillos, tomato, the arbol chile if using, and the salt with the anchos and their reserved liquid until smooth, 1-2 minutes. Transfer to a bowl and let sit at room temperature for about 30 minutes so the flavours meld, then season to taste with salt, cider vinegar and sugar, if using.

Shred the lamb and finish the broth. Lift the lamb onto a board. Pour the juices collected on the plate into the Dutch oven, discard the ramekin, onion, carrots and bay leaves, and bring the broth to a simmer over medium heat. Slice the lamb crosswise into 1.3 cm pieces, transfer to a bowl with 120 ml of the broth, and break it up into bite-sized pieces with tongs. Season the lamb and the broth with salt to taste.

Serve. Pile the lamb onto a serving platter and ladle the broth into individual bowls. Serve with the tomatillo salsa, warm tortillas, chopped onion, radishes, cilantro and lime wedges alongside.