My lovely Husband the TF cook says this...
All of the chicken... meaning any left overs... anything. Grass fed beef as well. I prefer (mama here... the beef). Knuckles, soup bones... any scrap, trimmings from a reliable source.
It does not hurt to break open the "big" bones, meaning... the chicken legs how they are sealed... snap them in half to find the marrow.
Carrot, celery, onions, bay leaves, cracked pepper corns, thyme, parsley for both. You would ideally brush the beef bones with a tomato product and roast them (if raw). We do a 24 hour + at home but you can be successful in 12 hours.
My Husband's teacher always said..... "Skim the stock with a skimmer, let it simmer. Never boil". It smells so good in your home!
Hope this helps!
Let us know how it goes!
How to store?