Tip the flour onto a plate, pour the egg yolks onto a shallow dish or plate and scatter the breadcrumbs onto a separate plate.
Dust the prawns first in the flour, then coat with the beaten egg and finally roll in the breadcrumbs until evenly covered.
Heat the vegetable oil in a deep heavy-bottomed saucepan until a breadcrumb sizzles and browns when dropped in it. (CAUTION: hot oil can be dangerous - do not leave unattended.) Add the breaded prawns to the hot oil and fry until golden-brown. Remove with a slotted spoon and drain on kitchen paper. Serve at once.