Mix beef, breadcrumbs, egg, milk, salt, and pepper.
Form the mixture into 16 to 20 small meatballs.
Heat olive oil in a large skillet.
Brown meatballs for 8 to 10 minutes.
Remove meatballs and set them aside.
Sauté mushrooms and onions until they are browned.
Add garlic and cook for 60 seconds.
Stir in flour and cook for two minutes.
Gradually whisk in beef broth and Worcestershire sauce.
Scrape the pan to release all the flavor.
Return meatballs to the skillet and simmer.
Cook until meatballs reach 160 degrees internal temperature.
Stir in tempered sour cream on low heat.
Serve over egg noodles with fresh parsley.