Add water, fish sauce, and palm sugar; simmer until mixture is reduced slightly, 1 to 2 minutes. Stir in green onions, cilantro, and cornstarch; simmer until mixture is reduced to a sticky-sauce consistency, about 1 minute more. https://www.hungryhuy.com/ca-kho-to-recipe-vietnamese-braised-fish www.npfamilyrecipes.com/recipe/vietnamese-braised-fish-ca-kho-to