Begin by trimming any excess fat or silver skin from the beef cheeks and pat them dry with a paper towel. Allow them to rest at room temperature for 20 minutes.

While the beef is resting, prepare the vegetables by dicing the carrot, celery, and onion. Also, peel the garlic cloves and have the bay leaves and thyme ready.

In a large Dutch oven or a heavy-bottomed pot, heat some olive oil over high heat. Season the beef cheeks with salt.

Once the oil is hot, sear the beef cheeks until they are nicely caramelized on both sides. After searing, remove the cheeks from the pot and set them aside.

In the same pot, add the diced vegetables and the tomato paste. Cook them until they are soft, without browning.

Stir in the tablespoon of all-purpose flour and mix well. Then add the garlic, bay leaves, and thyme.

Deglaze the pot with the red wine and tawny port, bringing the mixture to a boil. If it's safe to do so, you can flambé to burn off the alcohol; if not, skip this step.

Add a cartouche over liquid, then Cover the pot and transfer it to the oven, cooking for 3.5 hours at 300°F (150°C).

After cooking, remove the pot from the oven and place the beef cheeks in an oven-proof dish to keep them warm.

Strain the sauce from the pot and transfer it to a saucepan. Reduce the sauce over low heat until it becomes glossy and reaches the desired consistency. Add butter. Use cornflour to thicken if required.

Finally, season the sauce with salt and pepper, mix well, and serve.