01 - Generously season beef chunks with salt and pepper on all sides.
02 - Heat a large skillet over medium-high heat. Sear beef on all sides until browned, about 3-4 minutes per side. Transfer to the slow cooker.
03 - In the same skillet, add onion, carrots, and celery. Sauté for 4-5 minutes until softened. Add garlic and cook for 1 minute more.
04 - Stir in tomato paste and cook for 1 minute. Pour in red wine, scraping up browned bits from the pan. Simmer for 2 minutes.
05 - Transfer vegetable mixture to the slow cooker. Add crushed tomatoes, beef broth, oregano, thyme, bay leaves, and red pepper flakes. Stir to combine.
06 - Cover and cook on low for 8 hours (or high for 4-5 hours) until beef is fall-apart tender.
07 - Discard bay leaves. Shred beef using two forks and stir back into the sauce. Adjust seasoning if needed.
08 - Cook pappardelle according to package instructions. Drain and toss with a little sauce to prevent sticking.
09 - Serve beef ragu over pasta. Garnish with fresh parsley and Parmesan cheese.