Heat oil in a large flameproof casserole dish; cook lamb in 2 batches until browned. Remove lamb and add leek and carrot; stir over a medium heat for 5 minutes or until leek has softened. Add garlic and cook, stirring 1 minute longer. Add wine and simmer 3 minutes. Stir in tomatoes, stock, sun-dried tomatoes and bay leaves. Return lamb to dish and stir to combine.
Cover and place in oven. Cook for 2 hours, turning lamb shanks halfway through cooking time.
Remove lamb from sauce and cover with foil to keep warm. On stove top, heat sauce to simmering. In a small bowl, blend cornflour with 1 tablespoon water and add to sauce; stir until thickened. Stir in olive pate. Serve shanks with mashed potato and sauce. Sprinkle with parsley.