The base of the sauce is an oxtail fond. Brown the oxtail tips, then add carrots, onion, leek, thyme, bay leaf, and at least one bottle of red wine. Let it simmer for 5-6 hours to develop a deep flavor.

Skim some fat from the top of the oxtail fond and heat it in a saucepan.

Add a sprig of thyme and some white peppercorns to the saucepan.

Slice a few mushrooms, then finely chop one garlic clove and a few shallots.

Add the sliced mushrooms, chopped garlic, and shallots to the saucepan and sauté until softened.

Pour in the red wine and let it reduce, allowing the alcohol to cook off and the flavors to concentrate.

Ladle the pre-made oxtail fond into the reduced wine mixture.

Balance the sauce with a splash of red wine vinegar to add a touch of acidity.

Let the sauce simmer gently and reduce further until it reaches your desired consistency.

Strain the sauce through a fine-mesh sieve into a clean saucepan to ensure a smooth texture.

Take the sauce off the heat and whisk in cold butter to mount it (monte au beurre), which gives it a glossy finish and creamy texture. Ox marrow can be used for an even richer flavor.

Finally, season the sauce with salt and freshly ground white pepper to taste.