In a large skillet, heat a bit of oil over medium-high heat. Brown the beef stew meat for about 5-7 minutes until all sides are browned. This step adds depth of flavor.
Transfer the browned beef to the crockpot. Add the chopped onion, minced garlic, sliced mushrooms, beef broth, Worcestershire sauce, dried thyme, salt, and black pepper. Stir to combine.
Cover the crockpot and cook on low for 6 hours, or on high for 3 hours, 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, in a small bowl, mix the cornstarch and water. Stir this mixture into the crockpot and let it cook for an additional 30 minutes to thicken.
Serve the beef tips over the cooked egg noodles. Garnish with fresh parsley if desired.