In a large pot, place rump roast, beef shanks, short ribs, and bouquet garni. Press 1 tsp of salt into each end of the bone marrow pieces and add to the pot, tucking them between meats. Add enough cold water to cover the meat, and bring to boil over high heat. Once boiling, reduce heat to medium and simmer for 2.5 hours, skimming the foam as needed.
Meanwhile, add the onion studded with two cloves, the carrots, the leeks, and the bouquet garni in the pot. Cook partially covered until vegetables are very tender, about 1 hour. Cook the rest of the root vegetables in their own pot to serve with the soup.
Remove the top layer of the vegetables from the pot and arrange them on a large serving platter. Remove the bone marrow and set aside. Remove all the meat, cut off and discard string from the rump roast, carve the meat and arrange on the serving platter with all the vegetables and bone marrow. Cover to keep hot.
Strain the broth through a chinois or colander, and discard the bouquet garni. Return the broth to the pot and skim off the fat. Season to taste with salt and pepper, and keep warm on low heat.
Serve the broth in a bowl with vegetables and meat.
Servings on the side: fleur de salt, cornichons, mustard.