01 - Generously season beef chunks with salt and pepper on all sides.
02 - Heat a large skillet over medium-high heat. Sear beef chunks on all sides until deeply browned, about 3–4 minutes per side. Transfer browned beef to the slow cooker.
03 - In the same skillet, add onion, carrots, and celery. Cook for 4–5 minutes until softened. Add garlic and cook for 1 minute until fragrant.
04 - Stir in tomato paste and cook for 1 minute to deepen flavor. Pour in red wine, scraping up browned bits from the pan bottom. Simmer for 2 minutes to reduce slightly.
05 - Transfer vegetable mixture to the slow cooker. Add crushed tomatoes, beef broth, oregano, thyme, bay leaves, and red pepper flakes. Stir well to combine all ingredients.
06 - Cover and cook on low for 8 hours (or high for 4–5 hours) until beef is fork-tender and easily shreds apart.
07 - Remove and discard bay leaves. Shred beef using two forks directly in the cooker, stirring it back into the sauce. Taste and adjust salt and pepper if needed.
08 - Cook pappardelle according to package directions until al dente. Drain well, reserving a small amount of pasta water. Toss pasta with a ladle of the ragu sauce.
09 - Plate pasta topped with generous portions of beef ragu. Garnish with chopped fresh parsley and freshly grated Parmesan cheese.