Epi-Food's bone broth

INGREDIENTS:

5 pieces of beef bone (important: marrowbone should be included)
1 tablespoon cider vinegar
2 liters of still water
1/2 head celery (optionally also celery stalks)
1 large red onion
2 cloves of garlic
1 tsp peppercorns
1 cm thick piece of ginger
6 carrots
1 stick of leek
1 bunch of parsley (smooth or curly)
3 bay leaves

as well:
sea salt 
1 pinch of nutmeg

PREPARATION:

1. If you like the taste of your bone stock very spicy, you can roast the beef bones for 30 minutes at approx. 200 degrees circulating air. If you prefer a mild, vegetable aroma you can skip this step.
2. Boil the beef bones in a pot with 2 liters of still water. Add apple vinegar and simmer for about 1 hour.
3. Wash all other ingredients thoroughly and add to the beef bone in the water. Let the broth simmer at low heat for another 3 hours. (The broth needs this much time to dissolve the collagen from the bones and pass into the soup water. If you have a Croq-Pot or Slowcooker you can also let it do the work).
4. At the end of the cooking time, take the vegetable and bone pieces out of the water and collect them in a sieve above the pot so that they can drain off. Here it is advisable to use a spoon to squeeze out the vegetables.
5. Season the soup with salt and nutmeg and pour it into one or more containers. The bone stock can be kept in the refrigerator for about one week. If you have prepared a larger quantity, you can also freeze it in portions. The soup can also be used to refine other sauces and soups. Bon Epi-tit!