Demi-Glace

1. Stage

Preheat the oven to 450 degrees F (230 degrees C). Place veal bones in a roasting pan.

2. Stage

Roast bones in the preheated oven until well-browned, about 1 hour 15 minutes.

3. Stage

While the bones are roasting, drizzle oil onto a baking sheet. Add onions, carrots, and celery, then spread tomato paste over top. Mix until vegetables are well coated.

4. Stage

Roast vegetables on another rack in the oven until well-browned, about 45 minutes.

5. Stage

Transfer vegetables and bones to a large stockpot. Pour 10 quarts water into the stockpot and set over medium-high heat.

6. Stage

Meanwhile, pour 2 cups water into the roasting pan used for the bones. Set the pan on the stovetop over high heat; bring liquid to a boil while scraping the browned bits of food off of the bottom of the pan with a wooden spoon. Pour liquid and browned bits into the stockpot.

7. Stage

Bring contents of the stockpot to a boil, then reduce the heat to low and simmer gently, skimming foam as necessary, until meat and all connective tissues are completely off the bones, about 18 hours.

8. Stage

Set a colander over a bowl. Ladle vegetables, bones, and meat into the colander. Discard vegetables, bones, and meat; return any broth to the stockpot.

9. Stage

Bring broth to a boil. Boil until broth reduces to approximately 1 gallon in volume, 30 minutes to 1 hour.

10. Stage

Strain broth through a fine-mesh strainer into a large container set in an ice bath; chill to room temperature, 30 to 45 minutes. Cover the container with a lid or plastic wrap, then chill in the refrigerator until demi-glace is cold and set, 8 hours to overnight.

11. Stage

Scrape and discard any fat from the surface. Turn demi-glace out onto a work surface. Cut into 16 blocks. Wrap each block in plastic wrap and store in a resealable plastic bag in the freezer. Chef John