The place is called Air Dogs I believe, if I remember correctly. (Not related to the Air Dogs just off the field at PWK.) This is just a little trailer (new, only about 2 months old, very well maintained) just at the base of the tower outside the airport perimeter fence. You could literally park the plane a few feet away and grab a bite. Relatively cheap as well, I think the Beef, chips and a can of soda is like $4.
I rent out of PWK when I'm not working the line at North American Jet.