Add the soup mix, beef broth, tomato paste and Worcestershire sauce to the slow cooker. Cover and cook on low for 8 hours.
Remove the lid and stir in the noodles. Cook an additional 15 to 20 minutes, until noodles are hot.
ADVERTISEMENT
Pro Tip: For a south-of-the-border variation, substitute a pack of taco seasoning for the onion soup mix.