Yes, Eli's does the cheesecakes on United, at least out of ORD. I think they are available somewhere at the airport, but they are always available at local supermarkets. If you have a craving, you just need to take the Blue Line from ORD 2 stops (to Cumberland). Just to the north of the expressway is Dominick's, which is a pretty good supermarket. Don't forget to buy a transfer when you leave the airport so you can get back to the airport (RT is $1.80). If you have some more time, Eli's has a cheesecake museum/factory (yes, really) not too far from the airport (roughly at Irving Park and Harlem). It would be a little complicated to get there on public transport (take blue line to Harlem, then a SB Harlem bus) but would be a pretty quick cab ride right from the airport (take a regular cab). I understand there are free samples, and on the way you drive right past the Maurice Lenell cookie factory on Harlem (ditto on the free samples, and it smells wonderful).