- Finely chop the onion, carrot, and celery. Add them to a large pot with a little oil and sauté until fragrant.
- Add the tomato paste, stir well, and cook for another 2 minutes.
- Pour in the red wine, bring to a boil, and scrape the bottom of the pot with a spoon. Cook until the wine is reduced by half.
- Add the beef stock, garlic, bay leaves, and thyme. Bring to a boil, then reduce to low heat, skimming off any foam. Continue simmering until the sauce thickens and reduces to about 200–250 ml.
- Strain through a fine sieve, discard the solids. Let cool completely, then transfer to an airtight container and store in the refrigerator.