Cut the fish into thick fingers of equal size. Combine the panko and polenta on one plate, put the beaten eggs on a second plate or shallow bowl and the flour in a third.
Season the fish strips, then coat them first in flour, then in the egg, shaking off any excess, before rolling them in the crumbs to coat.
Pour just enough oil into a wide frying pan to cover the base, then put on a medium to high heat until a pinch of panko turns golden in about 45 seconds. Fry the fish fingers for two minutes, until golden underneath, then turn and repeat on the other side.