Bring a large pot of salted water to a boil and cook the egg noodles according to package directions until just tender. Drain and set aside.
Melt the butter in a large skillet over medium-high heat. Add the beef strips and cook for 2 to 3 minutes until browned on the outside. Remove the beef to a plate.
Add the diced onion and sliced mushrooms to the same skillet. Cook for 4 to 5 minutes until the vegetables soften and the mushrooms release their liquid.
Stir in the minced garlic and cook for 30 seconds. Sprinkle the flour over the vegetables and stir to coat everything evenly.
Pour in the beef broth and Worcestershire sauce. Bring the mixture to a simmer and cook for 2 minutes until it thickens slightly.
Lower the heat and stir in the sour cream until the sauce is smooth. Return the beef to the skillet and season with salt and pepper. Heat through for 1 minute.
Serve the beef and sauce over the cooked egg noodles and sprinkle with fresh parsley.