Trim the lamb shoulder of excess fat and cut into 1-inch cubes.
Heat the olive oil in a heavy-bottomed pot or tagine over medium-high heat.
Sear the lamb cubes until browned on all sides, then remove from the pot and set aside.
In the same pot, sauté the diced onion, minced garlic, and sliced carrots for 5 minutes until softened.
Return the lamb to the pot and stir in the cumin, coriander, cinnamon, turmeric, sea salt, and black pepper.
Add the beef broth and chickpeas, bringing the mixture to a gentle boil.
Reduce the heat to low, cover with a tight-fitting lid, and simmer for 45 to 50 minutes until the lamb is tender.
While the lamb is simmering, prepare the couscous by combining it with an equal amount of boiling water in a small bowl, covering, and letting it sit for 5 minutes before fluffing with a fork.
Serve the lamb tagine over the fluffy couscous and garnish with a dollop of Greek yogurt and freshly chopped cilantro.