Methods

1. Place the lamb in a large bowl, drizzle with 1½ tablespoons extra virgin olive oil, and toss to lightly coat the meat in the oil. Sprinkle with Hawaij Masala and 1 tablespoon Surya Salt, and using your hands, massage the meat until evenly seasoned. Cover and refrigerate for at least 8 hours, up to 48 hours.
2. The day of cooking, preheat the oven to 350°F.
3. Heat the remaining 1½ tablespoons extra virgin olive oil in a Dutch oven or large, heavy-bottomed pot over medium-high heat. Working in batches, brown the seasoned lamb on all sides, 2 to 4 minutes on each side, transferring the browned pieces to a large roasting pan. When you’re done with browning the meat, reserve the pot for later use.
4. If using the optional dhungar method, place a piece of lump hardwood coal on an open gas burner and heat until red hot. Place a metal katori or piece of aluminum foil formed into a bowl in the pan with the browned meat. Place the piece of hot coal into the bowl and top with ghee — it will start smoking immediately! — cover the whole pan tightly with foil and let smoke while you cook the aromatics. 
5. Return the pot to medium heat, add 3 finely diced white onions, and cook, making sure to scrape up any browned bits stuck to the bottom of the pan and stirring occasionally, until softened and caramelizing around the edges, 12 to 17 minutes. Add the garlic, serrano peppers, and tomato paste and continue to cook, stirring frequently, until the garlic softens and the tomato paste turns a couple shades darker, 3 to 5 minutes. Add the tomatoes, chicken stock, dried chillies, tamarind concentrate, and black limes, if using, and continue to cook until the tomatoes start to break down, 3 to 5 minutes more. 
6. Uncover the lamb, if smoking it, and remove the bowl with the coal and ghee from the roasting pan. Pour the jammy onion mixture over the meat and add 6 cups hot water and 3 to 4 small bay leaves. Cover the pan tightly with two layers of aluminum foil and bake until the lamb is fall-apart tender and can easily be pulled apart with a fork, 3½ to 4 hours. About an hour before the lamb is done, give it a gentle stir, nestle in the halved, peeled potatoes, reseal, and continue to cook until the potatoes are tender and easily pierced with a knife.
7. Meanwhile, rinse 2 cups basmati rice until the water runs clear, drain well, and transfer to a medium saucepan. Repeat with the remaining 2 cups basmati rice, placing it in another pot. Set both pots aside.
8. Remove the cooked lamb and potatoes from the oven, leaving it on for later use. Using tongs, transfer the lamb and potatoes to a sheet pan, reserving the roasting pan. Pour 3½ cups of the lamb cooking liquid into one of the pots with the rinsed basmati rice. Stir in the yogurt, place over medium-high heat, cover, and bring to a boil. Reduce the heat and cook until the rice is ¾ of the way cooked through, 8 to 12 minutes.
9. At the same time, cook the other pot of rice. Add the green cardamom, cloves, cinnamon stick, remaining 1 teaspoon salt, and 4 cups water to the rice, cover, place over medium-high heat, and bring to a boil. Reduce the heat and cook until the rice is ¾ of the way cooked through, 8 to 12 minutes.
10. While the rice is cooking, crush the saffron in a mortar, add 2 tablespoons hot water and let it steep for 10 to 15 minutes.
11. To assemble, return the cooked lamb and potatoes to the roasting pan, arranging in a single layer. Lightly spoon the rice cooked in the lamb broth over in one layer, followed by the spiced rice. Spoon the bloomed saffron and water over the top of the rice, cover the whole pan with aluminum foil, and return to the oven until the rice is fully cooked through, 20 to 30 minutes. 
12. Meanwhile, heat ½-inch canola oil in a skillet over medium heat. Working in batches, fry the 2 thinly sliced onions until deep golden and crispy. (Keep in mind, the onions will continue to cook a little outside of the oil, so I like to pull them when they are light golden.)
13. To serve, spoon the rice, lamb, and potatoes onto a big platter, digging deep to get some of the sauce on the bottom, and layering it into a big, savory mountain. Sprinkle liberally with the fried onions, and serve with an assortment of sides, like sahawig (see below), chutneys, and katchumber salad.

To make the sahawig

1. Place all the ingredients in a food processor or blender and pulse until coarsely chopped. Then with the machine running, drizzle in the extra virgin olive oil in a slow, steady stream, and blend until smooth. Taste and season with salt, if necessary. If serving later, transfer to a container or bowl and cover with plastic wrap, pressing it directly onto the surface of the sauce to slow oxidation.