Put 1 big metal jugful (1½ pints) of water in a pot. Put the pot on the fire. Add salt and the pounded ingredients. Bring all this to the boil. Then add the pieces of fish, the eggplants and the mushrooms. When the fish is cooked, add padek or fish sauce and the phak tam nin. Taste and check the saltiness.
Transfer the contents of the pot to a bowl, garnish with the chopped spring onion leaves and serve with young cucumber.