Cook the egg noodles according to the package instructions and set aside.
Season the sliced beef with salt and black pepper.
Heat olive oil in a large skillet over medium-high heat.
Sear the beef for 1–2 minutes until browned, then remove from the pan.
Add butter, onion, and mushrooms. Cook until softened.
Stir in the garlic and cook for 30 seconds.
Sprinkle the flour over the vegetables and stir well.
Gradually pour in the beef broth while stirring continuously.
Add Dijon mustard and Worcestershire sauce.
Simmer for about 5 minutes until the sauce thickens.
Reduce the heat to low and stir in the sour cream.
Return the beef to the skillet and cook for 2–3 minutes without boiling.
Serve over warm egg noodles.
Garnish with chopped parsley and enjoy.