Preheat the oven to <temperature>250<unit>°C</unit></temperature>

Place <quantity>1<unit>kg</unit></quantity> of chopped cow foot into a baking pan

Add <quantity>750<unit>g</unit></quantity> of chicken feet and <quantity>1½<unit>kg</unit></quantity> of chopped oxtail. Roast for approximately 30m until deep golden brown

Chop <quantity>1<unit>stalk</unit></quantity> of celery

Chop <quantity>½</quantity> leek

Trim and chop <quantity>1</quantity> large carrot

Trim, peel, and roughly chop <quantity>1½</quantity> medium onions

Transfer all the vegetables to a baking pan and place in the oven with the meat. Bake for 20m until deep golden brown

Wrap <quantity>2</quantity> sprigs of rosemary, <quantity>2</quantity> sprigs of thyme, and <quantity>2</quantity> bay leaves with a twine. You can use a leek leaf to make a casing

Remove the meats from the oven

Remove the vegetables from the oven

Add the roasted bones and vegetables to a pot over medium-low heat

Add the wrapped herbs and <quantity>4<unit>L</unit></quantity> of water

Simmer the broth for 8h to extract the flavors and collagen. Skim off any foam that forms on the surface to remove any impurities

Strain the broth and discard the solids. The bone broth is ready

Add <quantity>2<unit>L</unit></quantity> of the Bone Broth to a pan over low heat

Let it boil for 20-25m until reduced to ⅓ of its original volume. Stir occasionally to prevent lumping

Turn off the heat and add <quantity>40<unit>g</unit></quantity> of cubed cold butter and black pepper to taste

Tilt the pan until the butter is completely melted, add the remaining <quantity>10<unit>g</unit></quantity> of butter and stir to melt and combine. The demi-glace is ready

Upgrade your cooking game with this classic French sauce base!