Season the beef cubes with salt and black pepper.
Heat vegetable oil in a large skillet over medium-high heat.
Add the beef cubes in batches and brown on all sides, about 3-4 minutes per batch. Transfer browned beef to the slow cooker.
In the same skillet, add chopped onion and cook for 3-4 minutes until softened.
Add minced garlic and cook for 1 minute until fragrant.
Pour in beef broth, Worcestershire sauce, dried thyme, dried rosemary, and add bay leaves. Stir to combine and bring to a simmer for 2 minutes.
Pour the mixture over the beef in the slow cooker.
Cover and cook on low for 7 hours or until the beef is very tender.
About 20 minutes before serving, cook the egg noodles according to package instructions until al dente. Drain and toss with unsalted butter to prevent sticking.
Remove bay leaves from the slow cooker.
In a small bowl, whisk together all-purpose flour and cold water until smooth to create a slurry.
Stir the slurry into the slow cooker and cook on high for 15-20 minutes to thicken the sauce.
Serve the beef and gravy over the buttered egg noodles.
Garnish with chopped fresh parsley before serving.