We had some friends offer to take is to breakfast and were surprised by this place. It's set in the middle of a beautiful park. It has a wonderful terrace with great views of the park and the Bosphorus beyond. The food was served buffet style and had too much to choose from. You won't be dissappointed if you wake up early and make the journey up this way. It's hard to get to unless you know the bus system well, so you might want to splurge and take a taxi.
Normally a great view means mediocre food, but this place was unexpectedly good. Everything was tasty, service was fine. You're in the middle of a stunning park, at the top of a hill, with a fine view of the Bosphorus. There's no liquor, and staff have little English, but it'll work out. Getting there: if you come off the boat, head right (North) to Kalamis Sk., and then take that left (West) to the park entrance. Fastest route is to keep heading West and climb straight up the hill. You can't miss Sari Kosk, a big wooden house, at the top. There's a big terrace out front with a snack bar. Ignore that. March up the steps, through the first floor, and up to the second floor where the restaurant is. If you're doing the hop-on-hop-off boat, Sari Kosk is something you can probably do comfortably within two hours.
We came here for brunch on a weekend and enjoyed our time. The open buffet was huge and had everything from cereal to baked goods. The only downside was that they do not make filter coffee and it gets extremely crowded after 11 on weekends. The price was also a bit high in my opinion.