1/ Boil 1.5 liters of water in a pot, put fish in and cook for about 10 minutes. Use a ladle to take fish out.
2/ Smash tamarind with a cup of hot water to extract tamarind juice. Add the extracted juce to a pot and bring to a boil. Season with stock granules (or salt) and sugar
3/ Add okra, cook for about 5 minutes. Then, add tomatoes and bananas, continue cooking for 5 more minutes.
4/ Add bean sprouts, taro stems and 3 chillies. Boil and flavor again. Add sow-leaf herbs, rice paddy herbs and fish. Then, remove immediately from heat.
5/ Serve hot with cooked rice and a dish of fish sauce and chillies.
The spices used to cook sour soup or tamarind, saw-leaf and taro stems can be bought at Asian food stores.