01 - Set the oven to 325°F.
02 - Generously rub the lamb leg with salt and freshly ground black pepper.
03 - Heat olive oil in a large Dutch oven over medium-high heat and sear the lamb until deeply browned on all sides, approximately 10 minutes. Remove and set aside.
04 - In the same pot, add onions, carrots, parsnips, celery, and smashed garlic; cook for 5 minutes until slightly softened.
05 - Stir in tomato paste and cook for 1 minute to develop flavor.
06 - Pour in red wine, scraping up browned bits from the bottom, and simmer for 2 minutes.
07 - Return the lamb to the pot, add stock, rosemary, thyme, and bay leaves, ensuring liquid covers halfway up the lamb, adding more stock if necessary.
08 - Bring mixture to a simmer, cover tightly, and transfer to the oven. Cook for 2 to 2½ hours until the lamb is tender.
09 - Remove lamb and vegetables to a platter. Skim excess fat from the sauce and reduce over stovetop if a thicker consistency is desired.
10 - Slice or shred the lamb, serve alongside vegetables, and spoon sauce over the dish.