In a large skillet, brown the beef stew meat over medium-high heat for about 5 minutes. Transfer the browned meat to the crockpot.
In the same skillet, add the chopped onion and sliced mushrooms. Sauté for about 3 minutes until they start to soften. Add the minced garlic and sauté for an additional minute. Transfer this mixture to the crockpot.
In a separate bowl, combine the beef broth, onion soup mix, Worcestershire sauce, dried thyme, salt, and pepper. Pour this mixture over the beef and vegetables in the crockpot.
Cover and cook on low for 6 hours or until the beef is tender.
About 30 minutes before serving, cook the egg noodles according to the package instructions. Drain and set aside.
If you prefer a thicker gravy, mix the cornstarch with a little water to create a slurry and add it to the crockpot during the last 20 minutes of cooking. Stir well.
Once the beef is tender, serve the beef tips and gravy over a bed of egg noodles. Garnish with fresh parsley if desired.