01 - Pat the lamb pieces dry with paper towels and season generously with salt and pepper on all sides.
02 - Heat olive oil in a large Dutch oven or heavy pot over medium-high heat. Brown the lamb in batches, ensuring all sides develop a deep sear. Transfer browned lamb to a plate and set aside.
03 - In the same pot, add onion, carrots, and celery. Cook for 6-8 minutes until softened, stirring occasionally. Add garlic and cook for 1 minute more until fragrant.
04 - Return the lamb to the pot. Add rosemary, thyme, and bay leaf. Pour in the red wine, scraping up any browned bits from the bottom of the pot. Simmer for 2-3 minutes to reduce slightly.
05 - Add crushed tomatoes and broth. Stir well to combine and bring to a gentle simmer.
06 - Reduce heat to low, cover, and cook for 2½ to 3 hours, stirring occasionally, until the lamb is very tender and the sauce has thickened. Remove herb sprigs and bay leaf. Shred lamb into the sauce using two forks. Adjust seasoning if needed.
07 - About 20 minutes before the ragu is ready, cook the pappardelle in a large pot of salted boiling water according to package instructions until al dente. Drain, reserving about 1/2 cup pasta water.
08 - Toss the pappardelle with the lamb ragu, adding reserved pasta water if needed to loosen the sauce. Serve hot, topped with grated Parmigiano-Reggiano and fresh parsley if desired.