• Wash the fish and pat dry with paper towels. Cut three diagonal slits into each side of the fish. Set aside.
• Dice the coloured peppers into 2-cm cubes. Peel and slice the onion into thin wedges. Slice the tomato into 8 wedges.
• Combine the sauce ingredients in a bowl.
  

Fry the whole fish:

• Heat up a wok over high heat. Pour in enough oil to fill the wok till 1/4 full. Allow the oil to heat up until very hot.
• Meanwhile, mix the potato starch and plain flour in a small bowl. Pat the fish evenly all over with the starch mixture, including the inside of the cavity and slits. Tap off the excess.
• When the oil is very hot, deep fry one side until light golden brown, or near to 80 percent cooked. Do not move the fish once it's in!
• Turn over and fry the other side. Again, don't move the fish. When near to 80 percent cooked, remove the fish with a slotted spoon. Wait for 15 seconds for the oil to get hot again.
• Put the fish into the hot oil again. This time, fry until the surface is golden brown and crispy.
• Turn over the fish and do the same with the other side. Remove the fish with a slotted spoon, and drain on a wire rack. Drain the wok of oil and clean it.

Cook the vegetables and sauce:

• In a cleaned wok, heat up 1 tbsp oil over high heat. Once the oil is very hot, fry the garlic and onions until fragrant.
• Add tomato, diced peppers, and pineapple chunks. Continue to stir fry until they start to soften and become aromatic, about 30 seconds
• Pour in the sauce mix and bring the mixture to a boil.
• Lower the heat until the mixture is at a gentle simmer. Then, stir in the corn starch solution. Allow the sauce to thicken until the consistency is like a thick glaze.
• Stir in the chopped chopped spring onions.
• Simmer for 10 seconds, then turn off the heat.
• Set the fried fish on a serving plate. Dish out the sauce over the fish, and garnish with chopped coriander or cilantro. Serve immediately.