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