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No cassava in Eastern European lands where I am from :D But I saw many cassava plants in rural Laos.

Thais and Vietnamese (I spent several years in these countries) usually don't put the cassava root (tuber) in main dishes... So I am not that familiar with it. As I remember I tried only one dish with cassava: a dessert, boiled cassava tuber (root) with grated coconut.

You can utilize anything from cassava leaves.

Adding fresh cassava leaves to salads possible?

Yes, cassava tubers are often made as a sweet and savory dessert with coconut. But I have also made cassava soup which you can find on my blog. There are so many preparations from cassava tubers.

For cassava leaves we usually enjoy them after boiling first, not for salads served fresh.