Why does yogurt split in a cooked dish?

Yogurt's body comes from milk proteins forming a loose network. As the temperature rises that network tightens and expels the water it held, leaving a grainy, watery pot.

Tempering prevents it. Beat an egg yolk or a teaspoon of flour into the yogurt to protect the proteins. Then add hot broth from the pot a ladle at a time; once the temperature gap has closed, the mixture goes back in.

The final rule: after the tempered yogurt joins the pot, the dish is never boiled, only brought briefly to heat while stirring. Yayla soup, mantı sauce and wedding soup all follow the same rule.