Marinate the basa fish fillets in a mixture of vinegar, dark soy sauce, and black pepper powder for 30 minutes.

Heat a flat skillet on medium flame with a few drops of oil.

Pan fry the marinated basa fish on both sides for a couple of minutes until cooked through.

Place the cooked fish on a serving platter.

Heat sesame oil in a skillet on medium-high flame.

Add ginger and garlic to the skillet and saute for 30 seconds.

Add finely chopped spring onion bulbs and saute for another minute.

Add salt, freshly cracked black pepper, soy sauce, and vinegar.

Add 1/3 cup of water and bring the mixture to a boil.

Combine cornstarch with 1/4 cup of water to make a slurry.

Reduce the flame and add the cornstarch slurry to the sauce.

Allow the black pepper sauce to thicken.

Pour the black pepper sauce over the pan-fried basa fish.

Serve immediately.