Place peeled and clean prawns into a mixing bowl. Add half a teaspoon of salt, a teaspoon of white pepper and a tablespoon of Shaoxing cooking wine to the mixing bowl and mix together until evenly combined.
Add 2 tablespoons of self-raising flour to the mixing bowl and mix together until the prawns are coated in flour.
In a large mixing bowl add self-raising flour and salt, mix till evenly distributed. Pour water into the bowl and mix together.
Leave the batter to rest for 5 minutes (this helps to remove lumps). After 5 minutes, add a teaspoon of vegetable oil and mix together.
Heat oil in a wok or pan over a medium heat. Coat a handful of prawns at a time in the batter.
Add the battered prawns into the oil and fry for 4 minutes or until the batter is golden. Cooked prawn balls will float to the top, if they’re not floating cook for an extra minute.
To make the sweet and sour sauce, place water, sugar, ketchup, pineapple juice and vinegar into a wok or frying pan and heat over a medium to high heat.
After 2 minutes, mix a small tablespoon of cornflour and a tablespoon of water in a mixing bowl and mix together. Add the cornflour mixture into the sauce and mix together. Leave the sauce to simmer for a further 1 to 2 minutes or until the sauce has thickened.