Dizi (also called abgoosht) is the definitive Iranian comfort food — a thick stew of lamb, chickpeas, white beans, potato, and tomato, cooked in a small clay pot (dizi) and eaten in a very specific way: you pour the liquid off first into a bowl as a soup, then use a metal pestle to mash the solids into a paste, which you eat with flatbread, fresh herbs, and raw onion. It is rich, warming, and unlike anything else in Persian cuisine.
Tehran has dozens of dizi restaurants, ranging from ancient establishments in the bazaar area to modern branches in the northern suburbs. The experience is essentially the same everywhere: you order by the pot (one pot serves one person), you are given a small instruction card if you look confused, and the food is consistently excellent. Look for any place with dizi or abgoosht in the name, or just follow the clay pots.