Slow cooking beef renders it very tender in this dish, perfect with tagliatelle.
Heat a large non-reactive casserole pan until hot, add the pancetta and fry for 3-4 minutes, or until the pancetta softens and the fat starts to melt. Add the mince in small batches and fry over a high heat until browned. Remove each batch of mince from the pan with a slotted spoon, set aside and keep warm while you fry the remaining batches.
Add the olive oil and butter to the pan in which you cooked the beef, then add the onion and fry gently for 1-2 minutes, or until softened. Add the carrots and celery to the pan and cook for another minute.
Stir in the browned mince, then add the milk and bring to the boil. Reduce the heat and simmer for 5 minutes.
Stir in the tomato purée and cook for a further minute. Add the red wine and simmer until the volume of the liquid has reduced by one quarter.
Add the beef stock and return the ragu to the boil. Season, to taste, with salt and freshly ground black pepper. Reduce the heat and simmer for 1½-2 hours, or until the ragù has thickened and the mince is tender.
Mix the tagliatelle with a little of the ragù.
To serve, pile the tagliatelle onto each of four plates then top each serving with another generous spoonful of ragù. Sprinkle with some freshly grated parmesan.
