Wash potatoes thoroughly and cook in boiling water for 10-15 minutes. Clean, wash and quarter the radishes. Wash herbs and pat dry. Put some parsley aside for garnishing, chop the rest finely.
Cut the chives into small rolls. Whisk vinegar, salt, pepper and sugar. Stir in 2 tablespoons of oil in a thin stream. Mix with parsley and radishes and set aside. Peel onions and cut into fine rings.
Wash the liver, pat dry and cut each slice into 3 pieces. Drain potatoes, rinse with cold water and peel. Heat 2 tablespoons of oil in a pan. Fry the liver for 2-3 minutes on each side.
Remove, season with salt and pepper and keep warm. Fry onions in hot frying fat until golden brown. Take them out and fry the potatoes briefly in the frying fat. Season salad once again. Arrange liver with onions, potatoes and salad.
Add the sour cream and sprinkle with chives. Garnish with parsley set aside.