01 - Preheat the oven to 300°F or set your slow cooker to low.
02 - Heat olive oil in a large ovenproof casserole or skillet over medium-high heat. Season beef shin with salt and pepper, then brown the pieces in batches until evenly colored. Remove and set aside.
03 - In the same pan, add onions, carrots, celery, and garlic. Sauté for 5 minutes until they begin to soften.
04 - Return beef to the pan, pour in red wine, and simmer for 2 minutes to deglaze the pan.
05 - Pour in beef stock, add thyme sprigs and bay leaves, and bring to a gentle simmer.
06 - Cover the casserole and transfer to the oven or slow cooker. Cook for 3 to 3½ hours in the oven or 7 to 8 hours on low in the slow cooker, until beef is tender and sauce has thickened.
07 - Remove thyme sprigs and bay leaves. Adjust seasoning with salt and pepper if necessary. Serve hot.