The place sells some stuff that's non-vegan (like chocolate cake) and I can't vouch for every menu item as my Turkish is pretty awful. The staff had no idea what 'vegetarian' meant when I went in there, they just serve cigkofte.
The Durum Cigkofte, which traditionally is made from raw mince and wrapped in soft flat bread, is made from walnut - and it's pretty delicious! One durum cigkofte (without ayran yogurt drink) is 3.50t.
A snack more than a meal, but pretty good for that.
Cons: The cigkofte 'doner' looks scary., Only four or so items on the menu.