I can tell you, as I made this for the blog, the house smelled rich and sweet... and better than a pie in the oven! It takes a while to make it the way I describe, but you can take the short cut and simmer it on the stove for 3-4 hours until the marrow melts into the broth. I often make a slighter version by getting a beef shank and braising it, then cooking it till the marrow and meat are falling away tender.
Grass fed Beef Bones with marrow
Veggies like carrot, onion, celery, etc...
Lasts 7-10 days in the fridge.