01 - Bring a large pot of salted water to a boil. Cook egg noodles according to package instructions. Drain and set aside, optionally tossing with a little butter.
02 - Season beef strips with salt and black pepper evenly.
03 - Heat 1 tbsp butter in a large skillet over medium-high heat. Add half the beef and sear until browned, about 1–2 minutes per side. Remove and repeat with remaining beef.
04 - Reduce heat to medium. Add remaining 1 tbsp butter. Sauté onion for 3 minutes until translucent. Add garlic and mushrooms; cook 5–6 minutes until mushrooms are golden and liquid evaporates.
05 - Sprinkle flour over vegetables and cook, stirring constantly, for 1 minute.
06 - Gradually stir in beef broth. Add Worcestershire sauce, tomato paste, and Dijon mustard. Scrape browned bits from the pan.
07 - Let sauce simmer for 3–4 minutes until slightly thickened.
08 - Lower heat and stir in sour cream until smooth, avoiding boiling. Return beef and juices to skillet; heat through for 2–3 minutes.
09 - Plate beef stroganoff over egg noodles and garnish with chopped parsley.