I'm still fairly new to Chicago, so don't know what's available locally. I do know that the absolute best panettone I have ever tasted is made by Flamigni. (Having been force-fed more cheap panettone than I'd care to mention by over-enthusiastic
nonni and other assorted
parenti in Italy, it took a lot to convince me this was actually an edible foodstuff at all, let alone love it.)
Flamigni is imported from Italy, but a quick look revealed it online:
http://www.gourmetitalian.com/flamigni- ... /t3916.htm. Don't bother with the 'special' ones with chocolate, cherries, etc., but if you ever find the Pandoro, buy all they've got!
Be warned: it's not cheap and you will never be able to go back, but if you're serious about panettone...