In a bowl, marinate the fish for 30 minutes with the ginger powder, garlic powder, onion powder, salt and black pepper.
In another bowl, create the sauce mixture with oyster sauce, light soy sauce, dark soy sauce, brown sugar, hoisin sauce, fish sauce.
Put beaten egg with a little water in a bowl and breadcrumbs in another bowl.
Dip each piece of fish in the egg and then breadcrumbs covering it completely. Repeat for all the pieces.
Heat oil in a wok and fry both sides of the fish until light golden brown (about 5 minutes). Set fried fish aside.
Empty the excess oil into a container.
In the wok, fry the minced garlic, diced ginger, bell pepper for 2 minutes. Add sauce mixture and let it simmer for 1 minute.
Slowly add corn starch slurry (using ¼ cup of water), stirring until it thickens.
Remove from the heat and add the fish, toss fish thoroughly in the sauce.