Spread the venison bones on a metal tray and toast them at 200 °C for 40 minutes. You could also pan fry them, but in the oven you can a more even result. Toast them till golden brown.
Meanwhile cut the onions in half and clean them. Then slice them in thin slices. Now also cut the leek in half and wash it well. The white part should already be clean, so focus on the green leaves. Then slice it in thin slices. After that cut the carrot in half and slice it as well. The final thing we need to cut is the mushrooms.
Now add a drizzle of oil to a pan and start pan frying all the cut vegetables. Start on a high heat and turn it down once it starts to color. Scrape the bottom of the pan well and continue till your happy with the color.
Once that’s the case deglaze the pan with the white wine. Reduce it for 90%.
Meanwhile cut the garlic in half and add it to the pan. Also add the thyme, the black pepper and the coriander seeds.
When the venison bones have a nice color add it to the pan as well and deglaze the tray with some water. Let this soak in the oven for a couple of minutes.
Meanwhile submerge all the ingredients in the pan with water and add the flavored water from the tray. Let this simmer on a low heat for at least 12 hours. I left it simmering overnight and if needed added some more water. Just be sure the ingredients stay submerged.
After that drain the sauce on a sieve and let it drip for at least 30 minutes so you don’t waste a single drop.
Then reduce the sauce on a low simmer. While it’s reducing use a ladle to skim any fat and protein off the top.
Once you’re happy with the flavor and thickness pass the sauce through a fine sauce sieve once more.