I'm a native Californian who spent 8 years in Manhattan, and I haven't yet been able to shake my craving for those middle-eastern street-vendor chicken sanwiches -- You find them everywhere mid-town. You know, grilled chicken, onion, white sauce (what is it? not tahini, i don't think...?), hot chili sauce. But what are the spices? I think it's marinaded...Usually on pita, sometimes on a sandwich roll...
Can somebody give any advice on how to try to reproduce one? The spices and marinade are probably the biggest mystery. Also, what's the origin of these? Are they shawarma variants?