This much-loved baklavacı (baklava shop) opened in 1949 and was the first İstanbul branch of a business established in Gaziantep in the 1820s. There are other Güllüoğlu offshoots around town, but this remains the best. Pay for a porsiyon (portion) of whatever takes your fancy at the register, then order at the counters.
The most popular baklava flavours are fıstıklı (pistachio) and cevizli (walnut), but it's also possible to order a karışık (mixed) porsiyon. Many regulars order a serve of kaymak (clotted cream, ₺5) on the side. A glass of tea will take the edge off the sweetness. The su böreği (lasagne-like layered pastry laced with white cheese and parsley) here is good too.