In a large skillet, heat olive oil over medium heat. Add chopped onion and minced garlic, sautéing until the onion is translucent, about 3-4 minutes.
Add the ground beef to the skillet, breaking it apart with a spatula. Cook until browned, about 5-7 minutes. Drain excess fat if necessary.
Stir in the sliced mushrooms and cook for another 3-4 minutes until they are tender.
Sprinkle the flour over the beef mixture and stir well to combine. Cook for 1-2 minutes to eliminate the raw flour taste.
Gradually add the beef broth, Worcestershire sauce, and Dijon mustard, stirring constantly until the mixture thickens, about 5 minutes.
Reduce heat to low and stir in the sour cream. Cook for an additional 2-3 minutes until heated through. Season with salt and pepper to taste.
Meanwhile, cook the egg noodles according to package instructions. Drain and set aside.
Serve the beef stroganoff over the egg noodles and garnish with chopped parsley.