Tiny, no-frills Khoshbin is an institution among Tehranis, who cram onto the fast-turnover tables for an authentic Gilaki (food from the Gilan region) lunch. Try the mirza ghasemi (mashed eggplant, squash, garlic, tomato and egg), kuli (carp roe), zeytoun parvardeh (green olives marinated in pomegranate molasses, walnuts and herbs) and particularly the fried whole fish.
Usually known as Hassan Rashti, after the restaurant's founder, it's next to the Mikhak shoe shop.