2. Add the onions and cook, stirring occasionally, until they turn translucent, about 5 minutes.
3. Season the lamb well with salt and black pepper. Turn the heat to medium-high and sear the lamb cubes well on all sides.
4. Add the cayenne pepper, ginger and turmeric. Turn the heat to low, add the beef broth, cover the pot and cook for 45 minutes.
5. Remove the cover from the stew and add the carrots and zucchini. (Add a little water if the stew is too dry.) Cook for 20 minutes.
6. Meanwhile, make the couscous. Place a shallow metal colander inside a heavy-bottomed pot with a tight-fitting lid. If the colander's holes are big enough for the couscous to fall through, line it with a piece of dampened cheesecloth. Add an inch of water to the pot. Bring the liquid to a simmer.
7. In a medium-size bowl, combine the couscous with the remaining oil and stir well. Pour the couscous into the colander, cover and steam for 20 minutes.
8. Remove the colander from the pot, pour the couscous into the bowl and stir in the cold water, breaking up all lumps with a fork. Return the mixture to the colander, set it in the pot and steam an additional 20 minutes.
9. Transfer the couscous to the bowl once again, stir in the salt and hot water, breaking up the lumps with a fork.
10. Pour the couscous back into the colander, cover and steam until tender, about 20 minutes.
11. To serve, mound the couscous in the center of warmed plates and spoon the meat and vegetables around it.