Rub the garlic bulb with your hands to remove as much of the outer paper as possible. Toast the peppercorns, coriander, and cumin lightly, then grind and reserve.
Cut the meat into bite sized pieces and season with 1 tablespoon of the salt.
Meanwhile, in a dutch oven, heat the lamb fat or oil until lightly smoking. It will seem like a lot of fat.
Brown the lamb in the fat, remove and reserve, then add the onion to the lamb fat, stir for a few minutes, and cook until translucent.
Add the stock, garlic bulb, barberries and spices, along with the lamb back to the pan, cover and cook at a gentle simmer for 30 minutes.
Meanwhile, rinse the rice in water until it runs clear.
Sweat the carrots on medium-high heat in a separate pan for 5 minutes, then add them to the pot at the 30 minute mark. Simmer gently for another 30 minutes, covered.
Next, push the lamb and carrots under the liquid to give the rice somewhere to go.
Drain the rice well, then spread on top of the lamb in the lamb-carrot mixture being careful not to stir.
Press down on the rice a bit, to make sure it's just barely covered with liquid. If for some reason your liquid cooked down too far, add just enough water so that the rice is barely covered.
Cover the pot and cook for another 20 minutes at a very gentle simmer.
Remove the lid, and, using a spoon, mound the rice carefully into a dome shape so the rice isn’t touching the walls of the pot (see picture)
Using a chopstick or the handle of a thin wooden spoon, make a few holes going down to the bottom of the pot to create a channel for the steam to release through, to help ensure a fluffy pilaf and allow the rice to finish cooking by steaming.
Remove pot to a trivet, wrap tightly in a thick towel, and allow the plov rest and steam for the final 20 minutes before serving.
To serve the plov, remove the lids and towel, remove the rice first using a spoon, then mound the meat on top, garnish with cilantro and the garlic bulb and serve immediately.