Dredge the fillets lightly, but thoroughly, with seasoned flour.
Heat the butter in a frying-pan and when hot, fry the fillets until golden brown and cooked through —about 7 min. Arrange the fillets on a hot dish.
Reheat the fat until it is nut brown in colour and then pour it over the fish.
Sprinkle the lemon juice and parsley over the fillets, garnish with lemon "butterflies" and serve at once.