For the beef, fill a large bowl with cold water, add a little white vinegar, then immerse the marrow bones in it and leave them to soak overnight in the fridge.
The next day, cut all the meat into pieces, put into a pressure cooker and cover with vegetable stock. Bring to a simmer and then skim off any foam from the surface.
Add the trimmed and peeled onions and carrots, bouquet garni, crushed garlic, cloves, peppercorns and salt.
Follow the manufacturer’s instructions for bringing the cooker up to pressure, then cook for 45 minuteson the ‘vegetables’ setting. Leave the pressure cooker to rest for 10 minutes, off the heat, before carefully opening.
To prepare the vegetables, drain the soaked bones and remove the marrow. Poach it for three minutes in some of the beef cooking liquid (from the pressure cooker), then put to one side.
Peel and trim the vegetables as required, leaving a little of the leaves on the carrots and turnips. Cook the vegetables in boiling salted water until tender, then refresh in cold water and drain.
Make the horseradish cream, by mixing the fromage blanc with the grated horseradish, chives and parsley. Season with salt and pepper.
To finish off and serve, skim the fat from the beef-cooking liquid, then strain through a fine sieve. Divide the meats and vegetables between four bowls or plates, and add a little marrow and broth to each one. Season with fleur de sel and roughly crushed black pepper. Serve hot with the horseradish cream.