Season the Beef
Pat the chuck roast dry. Season all sides evenly with salt, pepper, and garlic powder.
Layer in the Slow Cooker
Place the chopped onion in the bottom of the crockpot. Set the seasoned beef roast on top.
Add Liquids
Pour the beef broth and Worcestershire sauce over the meat. Cover with the lid.
Slow Cook Until Tender
Cook on LOW for 6–8 hours or HIGH for 4–5 hours, until the beef is fork-tender and easily shreds.
Shred the Beef
Remove the roast and shred it using two forks. Return the shredded beef to the slow cooker.
Add the Noodles
Stir in the frozen egg noodles. Cover and cook on HIGH for 20–30 minutes, or until noodles are tender.
Thicken (Optional)
If you prefer a thicker sauce, mix cornstarch with cold water to make a slurry. Stir into the crockpot and cook an additional 5–10 minutes until thickened.
Finish and Serve
Stir in butter if using. Taste and adjust seasoning. Garnish with fresh parsley and serve warm.