Barbara Lynch’s haute-cuisine mecca was an instant sensation when it opened in 2010. The parade of tiny, striking dishes! The feather-light glassware! The prices! And the place has only improved over time, from the stunning prix-fixe menus to the staffers who anticipate your every need. We’re not alone in noticing. In February the restaurant became Boston’s first Relais & Châteaux property, a distinction reserved for the likes of Eleven Madison Park and the French Laundry.