Ingredients

8 pounds of beef bones, a combination knuckle and marrow
1 Tablespoon oil
1 teaspoon kosher salt
1 teaspoon pepper
2 onions diced
4 carrots diced
4 celery ribs diced
head of garlic split
5-6 sprigs of thyme
3 bay leaves
6 oz tomato paste

Instructions

1. Heat oven to 400 degrees. Place bones on foil lined sheet pan.  Drizzle bones with oil, and season with salt and pepper.  Bake for 45 minutes.

2. Remove bones from oven and turn over.  Return bones to the over and bake for an additional 45 minutes.

3. After bones have finished roasting, place into large stock pot.  Take care to drain off as much pan drippings as you can from the bones.  Reserve pan drippings to roast vegetables in. Cover bones completely with water.  Bring to a simmer. Using a small ladle or a large spoon, skim any impurities from top of stock throughout the entire cooking process.

4. In roasting pan with the reserved pan drippings, place the onions, carrots, and celery.  Roast for 30 minutes, and then place vegetables into the stock pot.  Again draining off as much of the pan drippings that you can.  I used one of the Chinese Spider spoons.

5. To the stock pot add the garlic, thyme, and bay.

6. In a fry pan add 1 teaspoon oil and the tomato paste.  Cook for 2-3 minutes.  Add tomato paste mixture to the stock pot. Simmer for 48 hours, replacing water as needed.  Continue to skim impurities throughout cooking process.

7. After the cooking process is complete, strain the stock into new container.  Place in an ice bath.  When fat solidifies on the top of the broth, remove it.  Strain the stock using a cheese cloth and strainer into storage containers.  Place stock in refrigerator or freeze for later use.

https://www.youtube.com/watch?v=hutv-KtmJgw