• Searing the Oxtail: Generously season the oxtail pieces with salt and pepper. Heat olive oil in a wide, heavy-bottomed skillet over medium-high heat. Working in batches if necessary, sear the oxtail on all sides until a deep, caramelized crust forms. This browning step adds a robust depth of flavor that carries through to the finished dish. Set the seared oxtail aside.
• Preparing the Vegetables: While the meat is searing, chop the onion, carrots, and celery into uniform pieces for even cooking. Mince the garlic finely to help it melt seamlessly into the sauce. Once the oxtail is browned and removed from the skillet, proceed to the aromatics.
• Sautéing the Aromatics: In the same skillet used for browning the oxtail, add the chopped onion, carrots, and celery. Cook over medium heat for around 5 minutes, stirring occasionally, until the vegetables begin to soften and release their aroma. Stir in the minced garlic and tomato paste, continuing to cook for 1 to 2 more minutes, allowing the tomato paste to darken and the garlic to become fragrant.

Cooking

• Assembling the Slow Cooker: Transfer the seared oxtail and sautéed vegetables into the slow cooker. Pour in the beef broth and add bay leaves, thyme, and rosemary. Stir gently to blend the ingredients, ensuring the meat is well nestled in the liquid and aromatics.
• Slow Cooking: Cover the slow cooker and set it to low heat. Let it cook undisturbed for 8 to 10 hours, until the oxtail is buttery-tender and the meat easily pulls away from the bone. If time is limited, the high setting may be used for 4 to 6 hours, though low and slow is recommended for the most succulent results.

Finishing Touches

• Adjusting the Seasoning: Once the cooking time is complete, taste the broth and adjust the seasoning with additional salt and pepper if needed. If the sauce is thinner than desired, carefully remove the oxtail and simmer the liquid on the stovetop until it reduces to a more concentrated consistency.
• Serving: Plate the oxtail over creamy mashed potatoes, steamed white rice, or alongside a thick slice of rustic bread—something hearty enough to soak up the savory sauce. Sprinkle with freshly chopped parsley just before serving for a vibrant pop of color and a touch of freshness.