Instructions

1. Preheat the oven to 430 F (220 C).
2. Spread the bones out on a large roasting tray and place in the oven for 45 minutes, turning the bones after 30 min. They should be dark golden brown.
3. At the same time, add the olive oil to a large frying pan and sauté the chopped onion, celery, garlic, and mushrooms until caramelized.
4. Add the caramelized vegetables and roasted bones to a large stockpot. Scrape the roasting tray and the rendered fat from the bones and add to the pot.
5. Fill the pot with the 3 liters of cold water and bring to the boil, skimming off and discarding any foamy impurities that gather on the surface.
6. Place a lid on the pot and reduce to a low simmer.  Simmer for 1 hour.
7. Remove all the bones and vegetables by pouring the stock through a strainer. Reduce the liquid stock further over moderate-high heat until the stock reduces to approx. 16 fl oz (480 ml) – this can take a while, so keep the lid off and check on it regularly.  Near the end, add in the rosemary and thyme for 10 minutes.
8. Add the 2 egg yolks to a large bowl and whisk well.  Slowly add 1 Tablespoon of the stock at a time into the egg yolk mixture.  Keep whisking.  After you’ve got about a cup of egg mixture, tip the mixture back into the rest of the stock.  Whisk well and continue to whisk over a low heat until the sauce has thickened.
9. Season with salt and pepper, to taste.