Cook the egg noodles according to the package instructions. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the chopped onion and cook for about 3 minutes, until softened.
Add the minced garlic and sliced mushrooms to the skillet, cooking for an additional 5 minutes until the mushrooms are tender.
Increase the heat to medium-high and add the ground beef to the skillet. Cook until browned, breaking it up with a spoon, about 5–7 minutes. Drain any excess fat.
Sprinkle the flour over the beef mixture and stir to combine. Cook for 1 minute to remove the raw flour taste.
Gradually add the beef broth, Worcestershire sauce, and Dijon mustard, stirring to combine. Bring to a simmer, cooking for 3–5 minutes until slightly thickened.
Lower the heat and stir in the sour cream. Cook just until heated through, about 2 minutes. Season with salt and black pepper to taste.
Serve the beef Stroganoff over the cooked egg noodles. Garnish with fresh parsley, if desired.