Stock is generally made from bones, and broth is generally made from flesh.
In both cases, they are often supported with aromatic vegetables, but in the case of stock, left unseasoned for maximum flexibility in recipes, whereas broth will usually contain at least salt and pepper..
A 3:1 ratio by volume of bones to mirepoix is a good starting point when making stock.
More mirepoix may compete with the protein, whether chicken or beef.
Many chefs prefer a higher ratio of up to 5:1 (bones:mirepoix), so that the chicken and beef flavors are more pronounced..
Bring to a boil on high heat and reduce to a low simmer.
If scum rises to the surface of the pot (this usually happens in the first half hour of cooking), skim off with a large metal spoon.
Let simmer uncovered at a low simmer for 4 to 6 hours.
Check every hour or so to be sure there is still enough water in the pot..
Chop onions, carrots and celery to a small dice and put in a large pan (I used a pressure cooker without the lid)
Cover almost to the top with water, allowing room for the water to boil so it doesn't over flow
Crumble in your stock cubes, add your salt and pepper
