Sift the Maizena and flour together and make a well in the middle, break the egg and pour the beer into the mixture and whisk until everything has just combined – it’s fine if the batter is a little lumpy.
Let the batter stand in a cool place for a few minutes and then heat the oil in a wok– check the oil by dropping in a bread crumb that should turn golden when dropped into it.
The oil must not be too hot, though – make sure the crumb is not dark brown, only golden.
Dip each prawn into flour to make sure it’s quite dry (it’s much easier to put some flour in a large Ziploc bag, shake up the prawns in the flour and then you’re ready to go.)
Dip the prawns in the batter and deep fry in the hot oil until it’s crisp and golden in colour.
Remove with a slotted spoon and drain on absorbent kitchen paper.