I have to say that Chicago has some very authentic Spanish places...but some of the more isolated and smaller ones are difficult to find because they do little advertising.
I really like Cafe Iberico (easy to find and well known, but very authentic) as well as Emilio's in Hillside.
Bravo just opened in Wicker Park, it's a great spot.
Arco de cuchilleros is another good one.
Let's discuss Chicago's Spanish restaurants here!!