Chicken broth from two roasted chickens

 If you bust up the bones, all of the marrow within them is pulled out into the liquid. Using a pressure cooker get the maximum marrow extraction and speeds the whole process plus it's fun. This whole thing could be done using a single pot and just boiling the chickens, but the resulting cooked chicken will have donated whatever flavor it had to the broth. It's how my mother made chicken and dumplings, which is fantastic. A good deal of marrow comes through the bones even if you don't break them up.

The broth chilled in a tall container forms a layer of fat at the top that is easily removed, a bowl, less easily because it's wider. I like to keep some of the fat because I like a bit of fat mixed into the broth. 

The layer underneath the fat is usually uniformly gelatinous. That giggly gelatin is aspic that formed from bone marrow. It melts when cooked and it's what spectacularly differentiates your homemade broth from commercial broth. You can use chunks of this chicken gelatin for bowls of broth, or for sauces, or wherever a flavor liquid is desired.