Make the flour slurry. Stir the tapioca flour and 25ml of water until well-combined.
Prepare the herbs. Separate the cilantro root from the stalk, and set it aside. Chop the cilantro stalks finely and set aside on a different plate.
Cut the red chilli and set them with the cilantro roots. Cut the garlic into half and set them with the chilli.
Cut the tofu into small cubes. Sprinkle some crispy flour and mix for them to absorb excess moisture. Set them aside.
Score the white pomfret fish. Make 3-4 scores in one direction, about 1.5cm apart, on one side of the fish, and repeat with another 3-4 scores across them. Turn the fish, and repeat on the other side. Marinate thoroughly with 1 tsp of salt - in all the scores and the stomach. Lastly, generously coat the fish with crispy flour on both sides. Set it aside.
Heat 500ml of cooking oil in a stainless steel pan over medium heat for 8 minutes, or until ready for deep-frying.
Meanwhile, make the chilli paste. Blend the cilantro root, cut chilli and garlic in a hand blender until well-combined and even in colour. Set it aside.
When the oil is ready for deep-frying, carefully add the tofu cubes and fry for 2 minutes. Stir them occasionally to separate them to prevent them from getting stuck to each other. After 2 minutes, remove them with a strainer, and set aside on a heat-resistant plate.
Next, carefully add the fish to the hot oil. As less oil is used, only the submerged part of the fish is cooked at a time. Use the turner to gently push the hot oil over the un-submerged side of the fish. Cook the fish for 5 minutes.
After 5 minutes, check the fish for crispiness and doneness. Then, flip the fish carefully. Let it fry for 4-5 minutes on the other side. Be sure to submerge the tail part of the fish into the hot oil as well.
After another 5 minutes, the fish should be well-cooked and crispy. Remove from the hot oil with a strainer, and switch off the heat. Rest it on a serving plate. Sprinkle all the fried tofu and sliced red onions all around the fish and leave aside.
Next, make the sweet, sour and spicy sauce. Add 2 tbsp of cooking oil from frying the fish into a non-stick pan. Switch on the heat to medium.
Add the blended chilli paste, salt, sugar and Maggi chilli sauce to the pan. Stir to mix for about 2 minutes, or until cooked and very fragrant.
Add concentrated tamarind juice and water to the mixture and stir to combine, until it becomes a rolling boil. Then, taste and adjust as preferred.
Add in the flour slurry, stirring immediately until well combined. Switch off the heat. Sprinkle most of the chopped cilantro, leaving some aside for garnishing. Stir until combined.
Pour the sweet, sour and spicy sauce all over the fish, tofu and red onions. Lastly, garnish with the rest of the cilantro and serve immediately.