Heat oil in a large pan over medium high heat. Sear and brown all sides of the lamb working in batches to not crowd the pan. Once browned, add the lamb to the slow cooker. In the pan that you seared the lamb in, sauté the onion and carrots until browned. Once browned add the vegetables to the slow cooker. To deglaze the hot pan that was used for searing, add the tomatoes and stock. Stir and scrape the liquid until everything is loosened and add the liquid to the slow cooker. Next add the ginger, garlic, Craisins, tomato paste, cinnamon, cumin, paprika, black pepper and cardamom to the slow cooker. Stir everything until well mixed. Add a lid to the slow cooker and cook on low for 6 hours (or high for 4 hours) or until the lamb is tender. When the lamb is almost ready, combine the onions, mint and lemon juice. To serve ladle the lamb mixture into bowls and top with the fresh mint salad.