Remove the shell from the scampi, discard the intestines. Rinse and drain properly on paper towels.
Whisk the egg with the cow’s milk. In a large baking bowl, combine baking powder, cornmeal, flour, Cajun seasoning, basil and celery salt. Mix with half the cow’s milk and egg mixture until smooth, then fold in the rest of the egg milk and let rest for half an hour.
Dip the crayfish tails in the batter and fry in batches in moderately hot oil until crisp and golden brown. Remove with a slotted spoon.
Drain briefly on paper towels and serve hot with a suitable sauce.
Our tip: Fresh basil is much more aromatic than dried!