In a bowl mix together with a wooden spoon
the cornflour, cold water and egg whites to
make a light batter.
Heat the vegetable oil in a deep-fat fryer
or pan until a cube of bread browns in
30 seconds.
Then simply dip the bunches of watercress
into the batter and carefully drop into the hot
oil, in batches, for 30 seconds or until crisp.
Remove and drain on kitchen paper. Season
with salt and serve.