Creating the incredible Slow Cooker Beef Manhattan is straightforward if you follow these simple steps:

1. Prepare the Beef: Trim any excess fat from the beef chuck and cut it into a few large chunks for easier cooking.
2. Sear the Beef (optional): In a skillet, heat olive oil over medium-high heat. Sear the beef chunks on all sides for added flavor.
3. Place in Slow Cooker: Transfer the beef to the slow cooker, followed by the sliced onion and minced garlic.
4. Mix the Sauce: In a separate bowl, whisk together the beef broth, tomato sauce, Worcestershire sauce, soy sauce, thyme, oregano, paprika, salt, and pepper.
5. Combine Ingredients: Pour the sauce mixture over the beef and onions in the slow cooker, ensuring everything is coated.
6. Set to Cook: Cover and cook on low for 5-6 hours or high for 3-4 hours, until the beef is tender and easily shreds with a fork.
7. Thicken the Sauce (optional): If desired, in the last 30 minutes of cooking, mix cornstarch with a little water and stir into the sauce to thicken it.
8. Shred the Beef: Once cooked, remove the beef from the slow cooker and shred it using two forks.
9. Return Beef to the Sauce: Place the shredded beef back into the slow cooker and stir to combine with the sauce.
10. Serve: Prepare the bread on plates and ladle the beef mixture on top. Garnish with fresh parsley, if desired.

These steps ensure you’ll end up with a delectable dish that’s bursting with flavor!