Peel the prawns but leave the tail on. Using a sharp knife, carefully devein them - it can be a bit fiddly and time consuming, but is definitely worth it (you could ask your fishmonger to do this bit for you).
Lay the prawns on a chopping board and, using a sharp knife, cut shallow slits on either side to flatten them out. Pat dry with kitchen paper.
Tip the cornflour in a shallow bowl and the salt. Mix to combine. Add the prawns and toss together so they are well coated. Set aside.
For the batter: in a large mixing bowl, mix together the plain flour, baking powder, garlic granules and salt. Give it a good stir and then add the sparkling water, followed by the ice cubes. Don't over mix - it's okay if there are lumps.
Fill a large deep-saucepan, casserole pan or deep-fat fryer ⅓ full of oil and heat until it reaches 190C. Line a plate or baking tray with kitchen paper.
One at a time, dip each prawn into the batter and gently shake off the excess. Carefully lower into the hot oil and fry for 2-3 minutes - or until crispy and golden brown. Once you get the hang of it, you can fry in batches of 3 or 4 at once - don’t do too many or you will overcrowd the pan.
Carefully remove the prawns from the oil using a slotted spoon and place on the kitchen-paper lined plate or baking tray to absorb any excess oil. Repeat with the remaining prawns.
Serve warm with sriracha mayonnaise, sweet chilli sauce or tentsuyu sauce. Enjoy!