To call this classic sauce base “kitchen gold” would be to overly flatter gold. Thanks to Squarespace for sponsoring this video!
8-10 pounds chicken wings
5-7 pounds beef shank and/or oxtail
4 red onions, peeled and cut in half
2-4 tablespoons tomato paste
Preheat oven to 400 F / 200 C convection (or 425 without convection). Oil a large roasting tray and put in the chicken wings. Oil another roasting tray or a rimmed baking sheet and put in the beef and onions. Roast both trays for about 45 minutes.
Remove the trays, and flip the beef and onions. Squeeze the tomato paste onto the chicken wings, and toss to coat them. Return the trays to the oven and roast them until everything is browned but not burned — about another 45 minutes.
Dump all the food and any juices into a large stock pot — at least 12 quarts. If any fond as developed on the trays, dry to deglaze it with some water and a wooden spoon, and add that liquid to the pot. Pour enough water in the pot to just barely submerge the ingredients.
Bring the pot to a bare simmer and hold it here for at least 12 hours, covered. Remove and discard the solids (no need to throughly strain at this stage), then bring the liquid to a boil and reduce the liquid by half, which should take about an hour. Transfer the liquid to a large bowl or other suitable container and add ice cubes until it’s no longer hot.
Cover and refrigerate until all of the fat has risen to the top and solidified — overnight at least. If the fat still isn’t solid, you can put it int he freezer for about a half hour — that should do it. Scrape all of the solid fat off the top and discard.
Return the liquid to the stock pot, bring to a boil, and reduce until it just achieves a syrupy consistency, stirring frequently once the liquid starts to get thick to keep it from burning. This could take up to two hours.
Let the demi-glace cool for a moment, then ladle it into ice-cube trays. You should get 32-48 cubes. Freeze them then transfer to a freezer bag. 1-2 cubes can be used to flavor and thicken enough pan sauce for 1-2 people.