Season the chuck roast on all sides with salt and pepper.
Optional: sear the roast in olive oil in a hot skillet for 2-3 minutes per side.
Add onion and garlic to the bottom of a slow cooker. Pour in broth, Worcestershire, Dijon, thyme, rosemary, and add the bay leaf.
Place the roast in the slow cooker. Cover and cook on low for 8 hours (or high for 4-5 hours), until very tender.
Remove the beef, shred it with forks, and return it to the slow cooker. Discard the bay leaf.
Whisk cornstarch and water together, then stir into the slow cooker. Cook on high for 10-15 minutes, until thickened.
Cook egg noodles in salted boiling water on the stove, drain, then stir into the slow cooker. (Or stir uncooked noodles into the slow cooker and cook on high for 15-25 minutes, until tender.)
Stir in sour cream (optional) with the slow cooker set to warm. Taste and adjust salt and pepper. Garnish with parsley and serve.