Wash the basa fish stomach, then scrub with salt, and rinse with water several times.
Soak the fish stomach with diluted vinegar water to eliminate the typical fishy smell.
Marinate the fish stomach with 1 tsp of fish sauce, 1/3 tsp of salt, 1 tsp of sugar, chopped shallot, pepper, 1/3 tsp chili powder (if any), 1/3 tsp turmeric powder. Wait for 5 minutes for the fish stomach to absorb the spices.
Rinse the mustard greens, squeeze tightly to remove the sour water, and chop.
Sauté onion until fragrant, then add the stomachs to stir-fry with high heat, then add pickled vegetables to stir-fry. Season to taste.
Turn off the heat, add green onion and pepper. The dish is best served with white rice.