Tian Bistro is adorable, with a young, well-intentioned, but inexperienced wait-staff in a very historic building. The menu is limited, see for youself here - http://www.taste-tian.com/fileadmin/user_upload/tian/bistro/at/vie-kh/dokumente/speisekarten/tian_b_karte_A5_1412_DEvfinal.pdf
To remove the butter, cream and cheese from all the offerings would leave a pretty undesirable, dry and tasteless result.
Our server didn't know what vegan food was. I would go for coffee or drinks, but not not when hungry!
Cons: Food, Service