Learned this method from the Ontario Science Center. They were demonstrating it.

Rich Broth

Cut some unpeeled onions in quarters and place on an edged baking sheet. Add any onion skins that fall off the onions. Add meaty bones (I have tried beef and pork) to the baking sheet. I add peeled carrots and celery also.

Broil in oven (shelf high up). As tips of meat and the onion skins blacken, turn them over. Broil until well blackened. (Yes, almost burned!)

When very well done put in large pot and cover with boiling water and some salt. Boil until the broth is very dark.

Strain and use to make soup or gravies. May be frozen.

You cannot imagine the beautiful flavor of this broth! It is good enough to drink as is!