America's been noshing it's way through a sandwich renaissance - with grilled-cheese cropping up on luxe menus, chefs reinventing fish sandwiches, etc. Now, Pittsburgh's signature sandwich - Primanti's - is making the rounds; restaurants and food trucks from SF to Brooklyn to LA have started serving the peculiar meat/fries/slaw sandwich. Native Pittsburgher Rico visits the original Primanti Bros. restaurant to learn why their concoction remains inimitable.