https://chefjeanpierre.com/recipes/quick-beef-stock
https://www.youtube.com/watch?v=Whtbrb_--Hc

1 lb yellow onion (large dice)
1 lb carrots (don't peel, 1/2 in slices)
1 lb celery (large dice)
1 leek (cut into 1 inch pieces and rinse to get rid of dirt)
6 sprigs fresh thyme
10 peppercorns
about 60 oz unsalted beef broth (enough to cover vegatables)

1. Heat oil in frying pan and cook onions until caramelized (about 10-15
   minutes)
2. Put the vegetables, cooked onions, pepper, and thyme into a stock pot and
   add enough beef broth to cover everything. Stir to combine everything.
3. Bring to a boil, and then reduce heat to a very low simmer. Cook for
   3-4 hours uncovered stirring occasionally.
4. Strain liquid and portion into freezable containers.

Will stay fresh in refrigerator for 4-5 days, or freeze for very long-term
storage.