Mackerel are cleared, add salt and sprinkle with lemon juice. Enough melts fat and fish fry on both sides until golden yellow. Arranged in preheated container and keep in a warm place. In the fat put the flour and diluted with a little water. To the resulting sauce add the grated feta cheese, white wine and cream. Season with salt, pepper and lemon juice and add the yolk. Pour over fish and top distributed stewed in butter mushrooms.