Blanch the marrow bones: Bring a pot of water to a boil. Once boiling, add the marrow bones and blanch for 15 minutes over medium heat, skimming off any foam. Remove the marrow bones and store them in an airtight container in the refrigerator. Strain the cooking water through a fine mesh strainer and pour it into a large pot.

Blanch the beef: Trim excess fat from the beef pieces. Place the beef in the pot with the reserved marrow bone cooking water. Add enough water to cover the beef by about 1/2 inch (1 cm). Simmer over medium heat for 1 hour, skimming off any foam.

Prepare the vegetables (while the beef is blanching): Peel the turnips and cut each into 4 pieces. Cut the core of the savoy cabbage into 4 wedges and secure each wedge with wooden skewers. Peel the garlic. Wash the celery stalks and cut each into 4 pieces. Peel the carrots and cut each into 3 pieces. Wash the leek, slice it in half lengthwise, tie it with kitchen twine, cut into 4 pieces, and secure each piece with toothpicks.

Prepare the aromatics (while blanching): Soften 2 leek leaves in hot water. Place the bay leaves and thyme on one leek leaf, cover with the other, and tie together with kitchen twine in the middle, at the ends, and between the two. Trim the bouquet garni with scissors and a knife. Peel the pearl onions and insert a clove into 4 of them. Peel the 2 garlic cloves. Peel the ginger and cut it in half.

Prepare the accompanying sauce (while the beef is blanching): Peel and finely chop half a red onion. Finely chop the chives. Finely chop the parsley leaves. In a bowl, combine the onion, chives, parsley, 2 tablespoons sour cream, 1 tablespoon mayonnaise, 2 teaspoons Dijon mustard, and 2 teaspoons balsamic vinegar. Season with salt and pepper. Mix well and refrigerate the sauce.

Add the vegetables: Add all the prepared vegetables and aromatics to the broth. Add more water if needed to cover. Season with salt and pepper. Simmer uncovered over low heat for 1 hour.

Final beef cooking: Remove the beef pieces. Strain the broth through a fine mesh strainer. Cut the beef into pieces small enough to be covered by the broth. Return the beef to the pot with the strained broth. Add salt and pepper if needed. Cover and cook over low heat for 2 1/2 hours. Add the marrow bones and continue cooking, covered, for another 15 minutes.

Cook the potatoes (2 1/2 hours after starting the final beef cooking): Place the 4 potatoes in a microwave-safe bag and microwave on high (1000W) for 5 minutes. Turn the bag over and microwave for another 5 minutes. Let cool in the bag for 5 minutes, then peel the potatoes.

To serve (per plate): Slice the beef and arrange in a deep plate. Ladle 2 large scoops of broth over the beef. Add 2 pieces of carrot, 2 pieces of turnip, 1 piece of leek, 1/4 of the cabbage, 3 pearl onions, 1 marrow bone, and 1 cooked potato. Sprinkle chopped parsley over the vegetables. Add 2 teaspoons of the accompanying sauce over the beef.