Place chuck roast in a slow cooker.
To a bowl, add hoisin, soy sauce, tomato sauce, chili garlic sauce, ground ginger, salt and pepper then whisk to combine. Pour over roast then cook for 4-5 hours on high or 7-8 hours on low.
Once roast is falling apart tender, remove from slow cooker and place on a sheet tray or large plate. Use two forks to shred making sure to discard any fat. Place shredded meat back in slow cooker with juices. (Keep slow cooker on WARM)
Combine cold water and cornstarch in a small cup then pour over meat. Stir to combine and leave lid off (while keeping warm) for 10-15 minutes.
Meanwhile, cook noodles according to package directions.
Serve shredded beef over noodles then top individual portions with cilantro and green onions. Add extra chili garlic sauce too for extra spice if desired.