What causes yogurt in sauces to split? How to prevent it?

Question

A lot of my favorite curry recipes have a yogurt based sauce in them, but on a pretty regular basis when I make them, the yogurt ends up splitting into basically curds and whey. What causes that, and how can I prevent it?

As an illustrative example, last night I made a simple tofu curry as follows:

1. warm evoo in a pan
2. add chopped onion, saute briefly
3. add curry seasonings, allow to warm/season the oil
4. add cubed tofu, toss to coat
5. cook for a while, tossing periodically to lightly brown the cubes
6. turn heat off
7. add plain greek yogurt
8. stir to combine

In the few minutes it took to finish the rest of the meal and start plating, the yogurt had separated so I had a clumpy, lumpy, yogurt soup instead of a smooth creamy sauce.

Answer

You are trying to add the yoghurt at too high a temperature. Let the dish cool to around 75 deg C before adding the yoghurt, and make adding the yoghurt the last thing you do before serving.

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