If you like having a Çay (tea) with your friends and playing backgammon, in a cosy place, close to Istiklal, our advice is to go there and to judge by own eyes this awesome place. 
There is 1 floor/terrace where you can find many sofas and smoke a nargile for 12TL (we recommand that you take the additional mint flavour for an extra 2TL). Obviously this café offers different kinds of tea, salep hot chocolate and more…
When you are on Istiklal, facing the Galatasaray high school, head to the right (Tünel direction). Then,after 100m you’ll see this pasaj on your right… it doesn’t look like much but there it is!
Enjoy!
After many disapointements in some restaurants, I finally found the right place to eat the perfect plate of Mantı for not more than 10TL!
Mantı are a kind of dumplings/raviolis (well basically macaroni stuffed with meat), topped with yogurt, garlic and a magical red sauce made of butter, tomato and red pepper. Actually, this red sauce is what I enjoy the most, so I ask the waiter to put little yogurt and lot of it! Try to ask more “Kırmızı sauce” (it sure isn’t the right way to say it, but it works so…).

Hala restaurant is on Istiklal Caddesi (map here).

The women you see on the picture are cooking Gözleme, the other specialty of this restaurant: these are fresh pastries filled with meat or cheese or spinach. Really good, served on a special wooden plate, and worth totally its price:5TL.
Enjoy and share!
Btw, if you know of any other good Mantı place, please let me know: bu-toyh@live.fr!
After an exhausting party on a saturday night, what is better than a good brunch with your friends on sunday?

At the Mek-Med on Istiklal (map here) and for 15TL (10TL on week days), you can get an unlimited buffet with many different foods like typical English breakfast or Turkish breakfast and many other choices.
Sometimes there are baklavas unlimited. Çay is also unlimited.
You have to pay more if you want orange juice or alcohol.
An advice: don’t arrive before 1:00pm because there are too many people at this time.
Do it, you can just enjoy!