Cut one of the onion in half, don’t peel. In a nonstick frying pan, ”burn” the onion. (The colour needs to be dark like a charcoal. This won’t give flavour, but will give a dark colour to your broth.)
In a very large, heavy-bottom casserole, add: Meats, (not the bones marrow) the burned onion, the other onion cut in half and poked with the cloves, the garlic head cut in half, bouquet garni, parsley, celery, black peppercorns, salt and cover with water, start the cooking, as soon as it starts boiling, lower the heat to a simmer and skim any foam that is floating.
Cook for 3 hours.
In the meantime: Peel carrots, turnips, potatoes and reserve. Clean the leeks under cold water, strain and dry them.
After 3 hours of cooking add all the vegetables (except the potatoes) and cook for 30 minutes.
Add the potatoes and the bones marrow, cook for 30 more minutes and let rest in the saucepan for 1 hour before serving.
Serve with pickles, fleur de sel and Dijon mustard and a fresh, crusty bread.