If desired, warm the canola oil in a large skillet over medium-high heat and quickly brown the chuck roast for about 1 to 2 minutes per side to deepen flavor.
Transfer the roast to the crock pot, then pour in the beef broth and scatter the chopped onion, minced garlic, Worcestershire sauce, and Italian seasoning on and around the meat.
Cover and cook on the Low setting for 6 to 7 hours or on High for 4 hours, until the beef is tender enough to shred easily.
Shred the beef directly in the crock pot using two forks, then season generously with salt and pepper.
Add the wide egg noodles along with any optional mushrooms or green peas, stirring well to mix them with the cooking liquid.
Switch the crock pot to High, cover it, and let the noodles cook for 10 to 20 minutes until they reach your preferred tenderness, checking often since cooking times vary.
Finish by stirring in either the heavy cream or the cornstarch slurry, and allow the sauce to simmer on High for a few minutes until it thickens and coats the back of a spoon.
Serve the dish piping hot in bowls, and garnish with fresh parsley if you like.