Trim excess fat from the beef and cut into 1-inch pieces.
Place the beef in the crockpot.
Add chopped onion and sliced mushrooms on top of the beef.
Mix beef broth, soy sauce, garlic, Worcestershire sauce, salt, and pepper in a bowl.
Pour the mixture over the beef and vegetables.
Cover and cook on low for 6-8 hours or high for 3-4 hours.
Check the sauce consistency about 30 minutes before serving.
If desired, mix cornstarch with water and stir into the crockpot for a thicker sauce.
Stir occasionally for even cooking.
Garnish with fresh parsley before serving.