The name of the food is La Majune - i dont think its spelt like that but the food is amazing - there are so many of these take away and eat in places where its advertised clearly in front that they make and sell La Majunes. These are large circular flatbreads which are smothered in a lamb sauce ( not spicy at all ) and lettuce tomatoes and cucumber are added along with their fantastic houmous - you then roll it up and enjoy. It's a lovely filler as a light lunch to get you going on your shopping spree as the eastern side of Istanbul is bargain central!
If you are staying on the western side of Istanbul and fancy something more authentic - then catch a boat marked USKADAR at the port of the sea of Marmara and it will take you straight over.
Google map: bit.ly/GT1tAS
Is this your business?