Peel and devein the prawns, but keep the tails on. Sprinkle prawns with salt. Set aside.
For the Batter:
Combine the flour, baking powder, ground black pepper. Add the egg, cold water, and fish sauce. Set aside.
Putting it All Together:
In a pan, heat oil until hot.
Holding the tail of the prawn, dip the prawn into the batter using a spoon. It is better if you use a spoon because the batter is quite thick and it is much easier to use it.
Deep fry the prawn for 2-3 minutes or until golden brown. Put only 3 to 4 prawns at a time to avoid overcrowding the pan. Continue until finished.