Wash the whitebait in a large bowl of water to remove any sand or dirt, then drain through a sieve. Spread the fish out on kitchen paper to remove excess moisture.
Mix all the ingredients for the batter together until smooth and thick. Add the whitebait, mix well and set aside for 10 minutes.
Heat the oil in a deep-fat fryer or a large, deep saucepan and drop the whitebait in one after another to prevent them sticking together (do this in batches so as not to overcrowd
the pan). Fry for about 2 minutes, until crisp, stirring occasionally.
Drain on kitchen paper and serve straight away.