Heat olive oil in a large skillet over medium heat. Add the chopped onion and minced garlic and sauté until the onion becomes soft and translucent.
Add the ground beef to the skillet and cook until browned, breaking it up into small pieces as it cooks. Drain any excess fat if necessary.
Transfer the cooked beef mixture to your slow cooker.
Stir in the crushed tomatoes, tomato paste, dried oregano, dried basil, salt, black pepper, beef broth, Worcestershire sauce, and bay leaf until well combined.
Cover the slow cooker and cook on low for 6–8 hours or high for 3–4 hours, allowing the flavors to meld beautifully.
About 20 minutes before serving, cook the spaghetti according to package instructions, then drain.
Remove and discard the bay leaf from the sauce. Serve the Bolognese sauce over the cooked spaghetti and sprinkle with freshly grated Parmesan cheese.
Enjoy!