The runaway favourite highlight of our recent trip to Istanbul was a walking culinary tour with Culinary Backstreets. This company operates several different walking tours in Istanbul; the one we chose was 'Two Markets, Two Continents'. It is truly an extraordinary way to experience Istanbul away from the tourists.
It was outstanding and I cannot recommend it enough. We were two groups of 6, (the maximum as many of the eateries are tiny) and both guides, Benoit & Gonca were local, knowledgable, passionate and huge fun. And of course, as well as the quality and variety of food it offers, we picked up a great variety of information about Istanbul life and history.
The day started at 9.00am and finished about 4.30pm. We did lots of walking but it was easy going and of course we had frequent stops for eating & drinking.
This route draws from the best-of list in the European side's Karakoy neighbourhood and the Asian side's Kadikoy, tied together by a ferry ride on the Bosphorus.
Kadikoy holds the highest concentration of traditional food shops & eateries in the city and encompasses Ottoman, Persian & Armenian Cuisines. The tour is a wonderful way to begin to understand some of the true building blocks of Turkish society, from nomadic tribal cooking to modern Turkish cuisine and the wonderful cultural melting-pot that makes up modern day Istanbul.
NB: I would recommend you take a Culinary Backstreets tour early on during your stay in Istanbul so that you can return to your favourite spots.