Season the beef with salt and pepper. Add in seasoned beef, crushed tomatoes, tomato paste, carrots, celery, garlic cloves, onion, and Italian seasoning into a slow cooker. Pour in the beef stock (or if you have some leftover red wine, use that). Cook on low for 6 hours (8 hours max). If you cook for longer, the beef will get mushy, so be careful! Right before serving, cook the pappardelle pasta in boiling water that has been lightly salted. Cook time varies based on packaging instructions. Take the beef out and shred it with two forks. Place back in the sauce. Serve beef ragu on prepared pappardelle pasta with shaved parmesan cheese.