Preheat oven to 320f (160c)
Pat the lamb pieces dry with paper towels and season generously with salt and black pepper.
Heat 1 tablespoon of olive oil in a pan over a medium-high heat. Brown the lamb pieces well on all sides, then set aside. You can do this in two pans to save time. Keep any rendered fat to add to the sauce.
Heat 1 tablespoon of olive oil in a heavy-bottomed ovenproof pot or Dutch oven over a medium-high heat.
Add the onion, carrot and celery and cook for 12-15 minutes until soft and slightly caramelized. Lower the heat if needed. Season with a couple of big pinches of salt and a good few cracks of black pepper.
Add the garlic and rosemary and cook for a further 2 minutes.
Add the tomato paste and cook, stirring for 2 minutes.
Add the wine and let reduce slightly for 2-3 minutes.
Add the stock and tomatoes and bring to a gentle simmer.
Return the lamb and any resting juices to the pot. Cover and place in the middle of the oven.
Cook for 2½ hours, checking after 2 hours. The lamb should be very tender and pull apart easily.
Remove the lamb from the sauce and shred with forks, then return it to the pot. Add the olives if using.
Simmer uncovered on the stovetop for 15-20 minutes to reduce and thicken the sauce if needed.
Cook your pasta in a large pot of well salted water, or prepare mashed potato or polenta if you prefer.
Add the cooked pasta directly into the ragu and let it bubble gently for a minute or two so it can absorb the sauce. You can divide it between pans if needed.
Add a splash of pasta water to loosen the sauce if needed.
Serve with lots of freshly grated parmesan.