01 - Generously season the beef chunks with salt and pepper.
02 - Heat olive oil in a large skillet over medium-high heat and sear beef on all sides until browned, approximately 2–3 minutes per side. Transfer seared beef to slow cooker.
03 - In the same skillet, sauté onion, carrots, and celery for 4–5 minutes until softened. Stir in garlic and tomato paste, cooking an additional 1 minute. Transfer mixture to slow cooker.
04 - Add crushed tomatoes, beef broth, red wine, oregano, thyme, basil, red pepper flakes if using, and bay leaves to slow cooker. Stir gently to blend ingredients.
05 - Cover and cook on low heat for 8 hours until beef is tender and easily shredded with a fork.
06 - Remove beef from slow cooker, shred using two forks, and return shredded meat to sauce. Discard bay leaves. Adjust seasoning with salt and pepper as necessary.
07 - Cook pappardelle pasta according to package instructions until al dente. Drain thoroughly.
08 - Toss pasta with ragu sauce or serve sauce over pasta. Garnish with freshly grated Parmesan cheese and chopped parsley.