Kotlety tsiplenokovo po-kievski (chicken kiev)

1. Wash and dry breasts, removing any connective tissue or skin.
2. Place smooth side on cutting board, and pound to flatten to about five millimeters thickness.
3. Combine butter with yolk of egg and divide into four equal parts.
4. Roll into sausage shapes seven to eight centimeters long.
5. Cover each with greasproof paper and chill until the pieces are very hard.
6. Wrap the breasts around each piece of butter, creating four parcels.
7. Dip in flour, one at a time.
8. Shake off excess flour and pat flat in the palm of the hand.
9. Dip in beaten eggs and roll in breadcrumbs.
10. Refrigerate for a few hours.
11. Deep-fry (in butter if possible) until golden brown.
12. Note: traditionally, chicken kiev is served with buckwheat kasha and peas served in small pastry shells.