Combine cumin and coriander in a small heavy skillet and cook over very low heat until fragrant and toasted, 5 to 7 minutes; cool 5 minutes. Transfer spices to a spice grinder with the cardamom and process until finely ground. Stir in the paprika and turmeric and set aside with the cinnamon sticks.
Preheat the oven to 300ºF. Heat 1 tablespoon of ghee or oil in a 4-quart enameled casserole or heavy saucepan over medium heat. Add one-fourth of the lamb, season with salt and pepper and cook, turning infrequently until nicely browned, about 7 minutes. Transfer the seared meat to a bowl and repeat with the remaining lamb in 3 more batches, adding more fat as needed.
Add the onion and another tablespoon of ghee to the same pot and cook over medium heat, stirring occasionally, until starting to soften, about 5 minutes. Add the spice mixture and cook 1 minute more. Return the seared lamb and any juices to the pot, along with the broth, cover and bring to a simmer.
Transfer the pot to the oven and braise gently until meat is tender, about 1 hour. Meantime, cook the couscous according to package directions.
Remove the lamb from the oven to the stovetop and stir in the apricots. Let sit for several minutes. (You can cook the stew up to 2 days ahead if desired.). Serve lamb atop couscous, and garnish with chopped cilantro or parsley.