Prepare all your ingredients by dicing the onion, mincing the garlic, and slicing the mushrooms.
In a large skillet, heat the olive oil over medium heat. Sauté the onion for about 3-4 minutes until soft and translucent. Add the minced garlic and sliced mushrooms, cooking for another 5 minutes.
Push the vegetables to one side of the skillet and add the ground beef to the empty side. Cook for about 5-7 minutes until browned, breaking it apart with a spatula.
Stir in the Worcestershire sauce, Dijon mustard, and beef broth. Bring to a gentle simmer and cook for about 5 minutes.
Mix flour with a few tablespoons of sour cream to form a smooth paste, then stir it back into the skillet with the beef and vegetables. Reduce heat to low and add the remaining sour cream, mixing well.
Cook the egg noodles according to package instructions. Serve the beef stroganoff over the noodles and garnish with freshly chopped parsley.