philadelphians haven't been this excited about a new york food export since cheesecake. the opening earlier this month of shake shack near rittenhouse square (2000 sansom st., 215-809-1742) brought the natives out in droves - perhaps out of curiosity, perhaps because of the burger joint's back story. shake shack originated as a hot dog cart in in manhattan to support the madison square park conservancy’s first art installation. in 2004, restaurateur danny meyer won the bid to open a permanent kiosk in the park, and from there he has added locations up and down the east coast. the chain has a gluten-free adjunct to the menu that includes bunless burgers and flat-top dogs, fries, frozen custard, shakes and wine. one of the managers at the philly location has celiac disease, and she let me know that the fries are prepared in a dedicated fryer that is not connected to the same oil line as other fryers. staff members also use a separate shake spinner and designated tins (black for malted,