Put the mushrooms in a heatproof bowl. Pour over enough boiling water to cover and allow to steep for 10 minutes. Drain, reserving 75ml of the liquid, and roughly chop. Place in the slow cooker.
Put the beef in a bowl, scatter over the flour and season well. Add the oil to a pan over a medium heat, then brown the beef all over and transfer to the slow cooker. You might need to do this in batches. Pour the wine into the pan used to brown the beef and let bubble until reduced by two-thirds. Transfer to the slow cooker.
Add the chopped vegetables, herbs, stock, chopped tomatoes and reserved mushroom soaking liquid to the slow cooker. Cover with the lid and cook for 4 hours on the low setting until the beef is tender and falling apart. Use two forks to shred the beef, then give it a good stir before serving.
Meanwhile, cook the pappardelle according to the instructions on the packet. Season the beef to taste and serve with the pasta and a sprinkling of freshly grated parmesan.