Trendy place with unique, good food in the Gold Coast?
It's been a while since I last tried it. Le Colonial on Rush street in the Gold Coast is French Vietnamese in a hip and trendy atmosphere. You asked for unique and trendy so I think this fits the part. Afterwards stop for a drink at Le Passage which is in the basement of Le Colonial...exit the building and enter Le Passage through the alley.
There are many other restaurants as well...Hugo's (same kitchen as Gibsons only less expensive and younger, Rosebud Steakhouse, Avenue's in the Peninsula Hotel is another hip and trendy spot, also try David Burke's for steak. Enjoy.
Although Le Colonial is billed as French Vietnamese, it's really just Vietnamese (the French part comes about because Vietnamese cuisine was influenced by the French in many ways). For true French-Vietnamese fusion try Le Lan - much more unique and trendy. Also, though it's a chain place, try Roy's. Hawaiian food is pretty unique here in Chicago - and it's very good. It's also "hip" (saw Alpana Singh at the bar there once).
I wouldn't describe Avenues as trendy or hip in the sense that it's a "scene" type of place, but it does have wonderful food, and a range of degustation menus at varying prices. It's certainly a meal you won't soon forget.