Prepare the beef: Season the chuck roast pieces generously with salt, pepper, onion powder, and thyme.
Layer in the slow cooker: Add the seasoned beef, beef broth, minced garlic, and heavy cream to the slow cooker. Stir everything to combine.
Cook: Cover and cook on low for 6-8 hours or on high for 3-4 hours, until the beef is tender and infused with flavor.
Thicken the sauce: About 30 minutes before the cook time ends, stir in the cornstarch slurry to thicken the sauce. Taste and adjust seasonings as needed.
Cook the pasta: Boil the pasta in a large pot of salted water according to package directions. Drain and set aside.
Combine: Add the cooked pasta and Parmesan cheese to the slow cooker. Stir until the pasta is fully coated in the creamy sauce and the cheese has melted.
Serve: Garnish with fresh parsley and serve hot. Pair with a side salad or crusty garlic bread for a complete meal.
