Trahanas is made by mixing flour, yoghurt or sour milk, and optionally cooked vegetables, salt, groats, and spices (notably tarhana herb), letting the mixture ferment, then drying, and usually grinding and sieving the result. The fermentation produces lactic acid and other compounds giving tarhana its characteristic sour taste and good keeping properties: the pH is lowered to 3.4-4.2, and the drying step reduces the moisture content to 6-10%, resulting in a medium inhospitable to pathogens and spoilage organisms, while preserving the milk proteins.

Tarhana is a dried food found in the cuisines of Southeast Europe and the Middle East. Dry tarhana has a texture of coarse, uneven crumbs, and it is usually made into a thick soup with water, stock, or milk. As it is both acidic and low in moisture, the milk proteins keep for long periods. Tarhana is very similar to some kinds of kashk.

The Armenian tarkhana is made up of matzoon and eggs mixed with equal amounts of wheat flour and starch. Small pieces of dough are prepared and dried and then kept in glass containers and used mostly in soups, dissolving in hot liquids. The Greek trahanas contains only cracked wheat or a couscous-like paste and fermented milk. The Turkish tarhana consists of cracked wheat (or flour), yoghurt, and vegetables, fermented and then dried. In Cyprus, it is considered a national specialty, and is often served with pieces of halloumi cheese in it. In Albania it is prepared with wheat, yoghurt and butter, and served with hot olive oil and feta cheese.