This is what I ate in Amsterdam (2 or 3 per day) "Shoarma is very thinly sliced lamb mixed w/some spices and then put into a warm pita w/some shredded lettuce and diced tomato. A sweet mayo-like sauce w/herbs was then offered to go with it or you could choose a VERY hot red chili sauce. I liked the mayo sauce."
Here in the Chicago area I've only had Shoarma at two places: The Pita Inn on Golf Road in Skokie (very disappointing) and the Falafel King on Oakton in Skokie (beef only, no lamb (owner says he has not sourced a lamb supplier yet), would rate it as good), these two places served their shoarma with a tahini sauce but neither of these places came even close to the heavenly shoarma of Amsterdam.
Any Shoarma fans out there and where are your places in Chicago that you like? I prefer lamb, but the beef is OK, seeing as the best shaorma I can find so far is a beef version at Falafel King