1. Season and sear the oxtails: Season the oxtails with salt and pepper, then lightly dust them with flour.
2. Heat the oil in a large pan over medium-high heat. Add the oxtails and sauté until golden on both sides. Remove them and set aside.
3. Sauté vegetables: In the same pan, add the diced onion, carrots, and celery. Sauté for 3-4 minutes until the onions are soft and translucent.
4. Add the garlic, thyme, rosemary, and tomato puree. Cook for another 2 minutes.
5. Deglaze and simmer: Pour in the white wine and let it bubble up and evaporate, scraping the bottom of the pan to release any browned bits. Add in the chicken stock and reduce by 1/2.
6. Return the oxtails to the pan, then add in enough water to cover the pan and bouquet garni. Bring to a boil.
7. Slow cook: Reduce the heat to low, cover, and let it cook very slowly for 2½ hours, or until the oxtails are tender.
8. Prepare persillade: While the oxtails are cooking, prepare the persillade. In a bowl, combine the finely chopped parsley, shallots, and tomatoes with rapeseed oil. Season with salt and lemon zest. Set aside.
9. Finish sauce: Once the oxtails are cooked, lift them out of the pan and set aside. Strain the cooking liquid through a fine sieve into a new pan. Bring the liquid to a boil and reduce it until it reaches a sauce-like consistency.
10. Serve: Glaze the oxtails with the reduced sauce. Serve the oxtails over buttery mashed potatoes, topped with the

Enjoy your braised oxtails with persillade and buttery mash!