Season lamb shanks with salt and pepper. In a Le Creuset or similar Dutch oven, heat olive oil to medium high heat until shimmering. Brown lamb shanks on all sides, about 2-3 minutes per side. Remove lamb shanks to a plate.

Pour jar of marinara and chicken broth into pot, scraping up and mixing in any browned lamb bits stuck to the bottom. Bring liquid to a boil, add lamb shanks back into pan. Cover, turn heat to medium low, and let lamb shanks simmer for 2-3 hours, flipping lamb shanks once. Remove lid, flip lamb shanks once more, and continue simmering for 1 additional hour, or until lamb is fork tender.

Serve lamb shanks, topped with pan sauce, garnished with chopped parsley.