Pat the Oxtail dry and season generously with Fine Salt and freshly crushed Black Peppercorns; lightly dust the pieces with Plain Flour, shaking off any excess.
Heat a generous splash of Extra Virgin Olive Oil in a large heavy-bottomed pot over medium-high heat and brown the oxtail in batches until deeply golden; transfer browned pieces to a plate.
Add the chopped Onion, Carrot and Leek to the pot and sweat gently until softened and beginning to caramelize, about 8–10 minutes.
Stir in crushed Garlic and chopped Tomato, cooking a few minutes until the tomato starts to break down and coat the vegetables.
Pour in Red Wine to deglaze the pot, scraping up any browned bits from the bottom, and simmer until the wine has reduced by about half.
Return the browned oxtail to the pot and pour in enough Beef Stock to nearly cover the meat; add Bay Leaves, Thyme and a few whole peppercorns if you like.
Bring to a gentle simmer, then reduce the heat to low, cover partially and cook very slowly until the meat is meltingly tender, about 2½–3 hours (or transfer to a low oven).
About 30–45 minutes before the end of cooking, add halved Potatoes so they cook through in the braising liquid without disintegrating.
When the meat is tender, lift it (and the potatoes) out of the pot, skim off excess fat from the surface, then boil the braising liquid until it reduces to a glossy, slightly thickened sauce; adjust seasoning with salt and pepper.
Return the meat and potatoes to the sauce to warm through, sprinkle with chopped Parsley and serve hot with the rich sauce spooned over—excellent with crusty bread or polenta.
