Put the rice in plenty of boiling salted water, cover and let it swell at low heat for about 15 minutes. Wash the meat, dab dry and cut into 3 to 4 wide slices. Cut lengthwise in each slice and unfold into small butterfly steaks. Heat oil in a pan and fry the meat in it on both sides for 2-3 minutes. Season with salt and pepper. In the meantime clean and wash the leek and cut it into fine rings. Take the meat out of the pan and keep it warm.
Add leek to the frying fat and fry. Season with tarragon, salt and pepper. Deglaze with stock and cook for 2-3 minutes. Add sour cream and lemon juice and stir in. Bring to the boil and sprinkle in sauce thickener while stirring. Bring to the boil again and season to taste. Arrange meat, rice and sauce on a plate and serve garnished with a slice of lemon and parsley