In a deep cooking pot pour the Canola cooking oil then add onions then sauté for 2 minutes.
Add the Miso paste and then mix with the onions and cook for another 2 minutes.
Pour-in the Patis (fish sauce) and water, and then bring it to a boil.
When its boiling, add the tomatoes and tamarind soup powder then cook for another 6 minutes.
Add the long green chilies and fish then in a low heat simmer for 20 minutes.
Turn off the heat, adjust the taste by adding more Patis if needed.
Place in a serving bowl while its hot, then serve.