First time I heard of this was on a Food Network show. It looked awesome to me, but I don't live in Chicago so I made my own version at home. So good! http://www.chicagopizzaandovengrinder.com/menu.htm
Chicago-Style Deep-Dish Pizza | Brown Eyed Baker. I omitted the cornmeal in the crust and replaced it with semolina flour. Makes 2 pies. I let it the second dough ball chill overnight and it was even better than the first pizza was.