Prepare the vegetables: Dice carrots, celery, parsley root, and onion. Dice the potato.

Cook the vegetables: Add the diced vegetables and potato to the soup stock and cook until tender.

Prepare the kidney: Split the veal kidney lengthwise, remove the fat and gristle, and soak it briefly in cold water.

Slice or dice the kidney: Pat the kidney dry and cut into very thin slices or dice it.

Sauté the onion: Cook the chopped onion in butter until barely tender.

Cook the kidney: Add the kidney to the sautéed onion and cook for a few minutes.

Create a roux: Sprinkle flour over the kidney and onion mixture, mix well.

Simmer the kidney mixture: Pour some soup liquid into the kidney and onion mixture, stir, and simmer gently for about 10 minutes.

Combine the mixtures: Add the kidney mixture to the soup.

Add pickles: Dice the dill pickles and stir them, along with their juice, into the soup.

Add sour cream: Add the sour cream to the soup, season with salt and pepper to taste, and bring to a boil.

Adjust tartness: If the soup lacks tartness, squeeze some juice from another pickle.

Garnish: Garnish with chopped dill.

Serve: Serve the Rosolnyk with pyrizhky.