Cut meat into ½ inch chunks.
In a large heavy skillet, melt 2 tablespoons of the butter.
Add onion and beef and brown on all sides over medium-high heat.
In a separate pan, prepare egg noodles per instructions on package and drain.
Set onions and beef aside.
In same skillet, add remaining 2 tablespoons butter.
Add sliced mushrooms and heat until brown on both sides. Add to the cooked beef.
In the same pan, add beef broth and flour to make a roux.
Cook over medium heat unit it just starts to bubble, then reduce heat to simmer.
Stir in sour cream, nutmeg, salt and pepper.
Stir until sour cream is completely dissolved.
Serve beef mushroom and creamy broth sauce over noddles.
Sprinkle with chopped parsley.