Heat the olive oil in a skillet over medium heat. Add the lamb shoulder cubes and brown them on all sides, then transfer the meat to the slow cooker.
Add the onion and garlic to the same skillet and cook until the onion softens. Scrape everything into the slow cooker with the lamb.
Stir in the walnuts, pomegranate molasses, beef broth, cinnamon, turmeric, salt, and pepper until well combined.
Cover the slow cooker and cook on low for 8 hours, or until the lamb is fork-tender.
Spoon the stew over the cooked basmati rice. Finish each bowl with pomegranate seeds and chopped parsley.