- Spray large Dutch oven with olive oil nonstick spray and set over medium-high heat. Sprinkle oxtails and beef with ½ teaspoon of salt. Cook oxtails and beef, in batches, until browned on all sides, about 8 minutes per batch, transferring meat to plate as it is browned.
- Spray Dutch oven with nonstick spray and reduce heat to medium. Add carrots, fennel, and onion; cook, covered, stirring occasionally, until carrots are tender, 8–10 minutes. Add garlic and thyme; cook, stirring, until fragrant, about 30 seconds.
- Stir tomatoes with their juice, broth, wine, oxtails, beef, remaining ¾ teaspoon salt, and the pepper into vegetable mixture; bring to boil. Reduce heat and simmer, covered, until oxtails and beef are fork-tender, 1½–2 hours. With slotted spoon, transfer oxtails to plate and let cool slightly (leave beef in pot).
- Stir parsnips and sweet potato into stew; simmer, covered, until potato is fork-tender, about 20 minutes.
- Meanwhile, remove meat from oxtail bones; discard bones. Stir oxtail meat into stew and cook until heated through, about 5 minutes longer. Skim off and discard any surface fat from stew before serving.
- Per serving: about 1 cup
To simmer the stew with superior results, cover the Dutch oven with foil, then add the lid to form an airtight seal in step 3. To completely remove the surface fat from the stew, refrigerate the stew overnight, then spoon oﬀ the solidified fat and discard. Reheat the stew over gentle heat.