Demi-glace sauce

Ingredients:

• 1/4 cup grapeseed oil
• 3.5 kg of veal bones (preferably joints)
• 6 liters of ice water
• 220 g onion, coarsely chopped
• 100 g carrots, peeled and coarsely chopped
• 100 g celery, coarsely chopped
• 170 g tomato paste
• 5 fresh sprigs of thyme
• 1 bay leaf
• 8 tbsp (2 l) red wine

Preparation:

1. Preheat oven to 230°C.
2. Pour oil into a metal roasting pan and place it in a preheated oven for 3-5 minutes. Arrange the bones in the roasting pan and roast until darkened, 30-45 minutes, turning occasionally to ensure even browning.
3. Transfer the bones to a saucepan large enough to hold 6 liters of water and the remaining ingredients. Use tongs to handle the bones to prevent fat from dripping into the pan. Add ice water and bring to a boil. Simmer the broth for 4 hours. Skim off any fat and foam from the surface occasionally.
4. While the broth is simmering, drain all but 1/4 cup of the fat from the Dutch oven. Heat the Dutch oven over high heat on the stovetop. Add the onion and carrot and cook until golden brown and caramelized. Add the celery and cook for another 10 minutes. Add the tomato paste, thyme, and bay leaf and cook, stirring regularly, until the tomato paste turns a brick-red color, about 15 minutes. Add 1 cup of red wine and whisk it into the vegetable mixture.
5. After the broth has been simmering for 4 hours, add the vegetable mixture to the pan. Bring the broth to a boil and continue simmering for another 2 hours.
6. In a separate saucepan, pour the remaining 7 cups of red wine, bring to a boil and simmer until reduced by half, 15 to 20 minutes.
7. After 6 hours of simmering, strain the broth through a Chinois sieve and combine the strained broth with the reduced red wine. Bring the broth to a boil, reduce the heat, and simmer until it coats the back of a spoon and the volume is about 2 liters (8 cups), about 1 hour. Season with salt and pepper to taste and strain the demi-glace through a Chinois sieve again.