• First make the garam masala. Puree poppy seeds and 1 tablespoon water in a spice grinder into a paste; transfer to a small bowl. Grind remaining spices into a powder; stir into the poppy seed paste.

Make the lamb (Nihari)

• Heat the oil and onion in a 6 quart saucepan (large enough to later hold the lamb) over medium heat. Once the onion starts to soften, lower the heat to medium low and cook until the onion is caramelized and a little bit crisp around the edges. This will take about half an hour. Once the onions are done, remove them with a slotted spoon and place them on a plate lined with paper towel, to absorb some of the excess oil. The onions will be used to garnish the lamb when you serve it. Discard all but 1/4 cup oil from the pan (reserve it for another use, if you like)
• Season the lamb shanks with salt and pepper. Brown the lamb in the same pot over medium to medium-high heat. This will take about 20 minutes to do all sides well.
• Once the lamb is browned, stir in the garam masala, the cayenne, garlic and ginger pastes, and about a teaspoon of salt. Cook for 1 to 2 minutes. Add 3 cups water and bring to a boil over medium-high heat. Reduce the heat to low/medium-low and cook covered until the lamb is falling off the bone, 5 - 6 hours. (Conversely you could transfer the whole shebang to your slow cooker now and cook on low for 6 or 7 hours)
• Using tongs, transfer the lamb to a bowl or platter and cover well with foil to keep warm. Stir flour, butter and 1/4 cup water together in a small bowl then add the mixture to the pan. Cook until the juices are thickened about 15 minutes.
• Pull the lamb off of the bone and using your hands or two forks, shred the meat. Return the lamb to the pan and stir to coat with the sauce.
• Garnish the lamb with the reserved onions, cilantro, julienned ginger, cilantro and, if you like, lime wedges and/or chilis. Serve with cilantro brown rice and warm naan.