Pat the beef dry with paper towel. Heat 1 tbsp olive oil in a large heavy-based pan over high heat until shimmering.

Working in two batches to avoid crowding, brown the beef on all sides until deeply golden, 6–8 minutes per batch. Transfer to your slow cooker.

Add the remaining oil to the pan, lower heat to medium, and cook the diced onion until soft and golden, 5 minutes. Add the garlic and cook for 1 minute until fragrant.

Stir in the tomato paste and cook for 1 minute. Pour in the red wine, scraping the base of the pan with a wooden spoon to lift any browned bits. Simmer until reduced by half, about 3 minutes.

Transfer the onion and wine mixture to the slow cooker. Add the carrots, celery, crushed tomatoes, beef stock, bay leaves, thyme, rosemary, dried chilli (if using), salt, and pepper. Stir gently to combine.

Cover and cook on low for 8 hours, or on high for 5 hours. The beef should be so tender it shreds easily when prodded with a fork. If there's excess liquid, remove the lid for the final 30 minutes of cooking to allow some evaporation.

Remove the bay leaves, thyme sprig, and rosemary sprig. Using two forks, shred the beef directly in the sauce until it breaks apart into fine strands. Stir well to combine—the sauce should coat the meat and be rich and clingy, not soupy.

Bring a large pot of salted water to a rolling boil. Add the pappardelle and cook until tender but still with a slight bite, 2–3 minutes (fresh pasta cooks quickly).

Drain the pasta, reserving 235 ml of pasta water. Return the pasta to the pot and add the beef ragu, tossing gently. If it looks dry, add a splash of pasta water, a little at a time, until the ragu coats the noodles silkily.

Divide among four warm bowls. Top with grated Parmesan and a scatter of fresh parsley. Serve immediately.