Season the beef cubes with salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat. Add the beef cubes in batches and brown on all sides, about 4-5 minutes per batch. Transfer browned beef to the slow cooker.
In the same skillet, add the diced onion and cook for 3-4 minutes until softened. Add the minced garlic and cook for 1 minute more. Transfer onion and garlic to the slow cooker.
Pour the beef broth and water into the slow cooker. Stir in Worcestershire sauce, dried thyme, dried rosemary, and bay leaves.
Cover and cook on low for 6 hours until the beef is tender.
About 30 minutes before serving, remove bay leaves from the slow cooker. Add the wide egg noodles to the slow cooker and stir to combine.
In a small bowl, whisk together cornstarch and cold water until smooth. Stir the cornstarch mixture into the slow cooker to thicken the broth.
Cover and cook on high for 20-30 minutes until the noodles are tender and the sauce has thickened.
Stir in chopped fresh parsley before serving.