Mix the flour, cornflour, chilli, zest and dill in a bowl.
Whisk in the water until you have a smooth batter.
Heat the oil to 170°C.
Put the prawns into the batter and then fry the prawns a few at a time.
Drain on kitchen paper and repeat until all prawns are fried.
Serve with a dip of the Jalapeno Relish.