Allow the lamb chops to marinate for at least 1 hour. Sear the lamb chops in a heavy skillet over high heat for 4 minutes per side, until nicely browned. Place the lamb chops and glaze in a baking pan, cover, and bake for 1½–2 hours, until the lamb chops are completely soft. To prepare the caramelized dates and leeks, heat the margarine in a sauté pan. To serve, plate a lamb chop with some of the glaze and garnish with a mound of caramelized leeks and dates.