1. Heat a dry wok over a medium heat. Add the salt and stir constantly for about 4 minutes, until the colour changes slightly. Transfer to a small bowl and mix with the five-spice powder and black pepper.
2. Pour some oil into a large pan until it is about one-third full and heat to 180C/350F or until a small piece of white bread dropped into the oil browns and rises to the surface in 1½ minutes.
3. Add half the prawns and fry for 30 seconds until they have curled up and turned pink. Remove and repeat with the remaining prawns.
4. Reheat the dry wok over a high heat. Add 2 tbsp of the spiced salt and cooked prawns, then flip the prawns over in the salt for 30-40 seconds so that it can permeate them. Tip on to warm serving plates and serve the remaining salt separately.