How to Make Beef Broth from Leftover Beef Bones

2 Tablespoons oil
4-6 pounds leftover beef bones and fatty meat or beef shank bones
1 onion, quartered
1/2 cup red wine
2 quarts water
1/2 teaspoon salt if needed may not need if using leftover bones and meat that were seasoned

Brown the bones and some fatty pieces of meat plus one onion cut in quarters in the oil. Remove them from the pan and add1/2 cup of red wine to the pan, stirring and cooking a few minutes until it is reduced to a syrupy looking concoction. Add the bones, meat and onions back to the pan, turned to low, covered, and cook for 20 minutes or so, letting them "sweat" for a bit, producing a dark rich looking liquid.
Add 2 quarts of water and bring to a very low simmer, leave the lid askew, and cook for 2 hours, checking periodically that the broth is at a low simmer. Taste and add salt if necessary.
Pour the broth into a large jar or other container, straining it through a fine meshed strainer. Chill overnight in the fridge and skim off any accumulated fat.