In a large nonstick skillet over medium heat, heat 1 tablespoon oil. Season lamb with salt and pepper. Cook, in batches if necessary, until browned on all sides, about 6 minutes. Transfer browned lamb to slow cooker insert.
Add remaining 1 tablespoon oil to pan (if necessary); add onion, garlic, ginger, cumin, coriander, cinnamon and cayenne. Cook until softened, about 8 minutes. Add broth and tomatoes; bring to a boil.
Add mixture to slow cooker along with chickpeas and raisins. Cover and cook on low for 5 to 6 hours, or high for 3 to 4 hours.
Remove lid; stir in chopped greens until wilted, about 1 minute. Serve with whole wheat couscous and a dollop of Greek yogurt.