In a slow cooker, mix together the beef, onions, garlic, carrots, potatoes, and celery.
In a separate bowl, whisk together the broth, wine, tomato paste, thyme, rosemary, salt, and pepper. Pour this mixture over the beef and vegetables in the slow cooker.
Cook on low for 8-10 hours or on high for 4-5 hours, or until the beef is tender.
In a small bowl, mix together the cornstarch and water. Stir this mixture into the slow cooker and cook for an additional 15 minutes, or until the sauce has thickened.
Serve the beef stew hot, garnished with chopped parsley if desired.