Prepare the batter:mix the flour and a pinch of salt in a bowl. Make a well in the middle. Pour in the oil, then gradually add 15 cl of lukewarm water, stirring with a spatula, to obtain a homogeneous paste. Let it rest for 2 hours in the refrigerator.
Meanwhile, prepare the tartar sauce:work the hard-boiled egg yolks with the mustard with a fork, gradually add the oil while whisking, then incorporate the herbs, capers and coarsely chopped gherkins. Adjust the seasoning.
When using the batter, gently fold in the beaten egg white. Heat the oil to 180°C. Line a baking dish with absorbent paper and preheat the oven to th.5 (180°C).
Remove the head of the prawns, dip them in the batter, then dip them (in small quantities) in the hot frying oil. Count 3 to 5 minutes of cooking, depending on the size of the shrimp. Drain them with a slotted spoon, then place them on the baking dish and keep them warm in the oven until you have cooked them all.
Present the scampi on a hot serving platter, garnish with slices of lemon and parsley leaves, accompany with the tartar sauce and serve immediately.
