Heat the oil in a large frying pan over a medium-high heat and fry the beef in batches until nicely browned. Remove from the heat and set aside.
Add the pancetta to the same pan and fry for 2-3 minutes. Add the onion, carrots and celery and fry for a further couple of minutes until they start to colour. Add the garlic, fry for 1 minute and then remove everything from the pan.
Add the wine to the pan and bring to the boil. Simmer for a couple of minutes, then remove from the heat.
Put the beef in the slow cooker, along with the pancetta, vegetables and wine. Add both tins of tomatoes. Cover and cook on low for 7 hours, adding the fresh rosemary half an hour before the end of the cooking time. Season with black pepper.
Meanwhile, cook the pasta according to the instructions on the packet. Divide between 6 bowls and top with the ragù. Sprinkle with parmesan shavings to serve.