Rinse the fish, make an incision along the abdomen. Remove bones and ridge, gently cutting the flesh with a knife. Remove the thin skin covering the fish and carefully cut the dorsal fins so that the fins remain interconnected. Rinse well again.
Salt and pepper on both sides. Lubricate with sour cream and leave for 20 minutes.
Beat the egg and spread over the surface of the fillet. Shake off excess eggs before frying.
Fry the mackerel schnitzel in a well-heated skillet in vegetable oil on both sides.