Salt and pepper the fish.
Fry fish in hot oil until golden brown. After frying, place on kitchen paper to drip of.
Cut onion in big slices, garlic in thin slices, chili in fine stripes. Using a mortar crush mustard seeds lightly.
Break fried fish into equal pieces and remove fishbones.
Heat in a wok 3 to 4 tbsp oil. Roast onions slightly.
Add garlic, tumeric, mustard seeds, chili and stir.
Add vinegar.
Add fish and season with salt to taste. Stir carefully until the fish is coated with spices.
In a jar, it keeps in the refrigerator for a few days.