Wash and cut the courgettes into 1cm batons.
Sprinkle the batons with salt then place in a sieve over a bowl and leave for 20 minutes to allow the salt to draw out the excess moisture.
Place the flour in a bowl and add in the sparkling water. You want a smooth runny batter almost like double cream.
In a separate bowl, whisk the egg white until you have stiff peaks then fold it into the batter.
Place a deep pan over a medium heat and coat the bottom with around two cm of vegetable oil. Heat to 180oc. Drop a piece of bread in and if it sizzles and colours in 15 seconds, the oil is ready to use.
Pat the courgette batons dry then toss in the batter and place in the pan to cook for just a minute or two.
Do this in batches so that you do not lower the temperature of the oil.
Remove and place onto kitchen paper to absorb any excess oil.
Sprinkle with sea salt, parmesan and lemon zest and serve immediately.