01 - Bring a large pot of salted water to a boil and cook egg noodles according to package directions. Drain and optionally toss with butter. Set aside.
02 - Season beef strips with salt and black pepper evenly.
03 - Heat 1 tablespoon butter in a large skillet over medium-high heat. Add half of the beef strips and sear for 1 to 2 minutes per side until browned. Remove and repeat with remaining beef.
04 - Lower heat to medium and add remaining 1 tablespoon butter. Sauté onion for 3 minutes until translucent, then add garlic and mushrooms. Cook, stirring frequently, for 5 to 6 minutes until mushrooms are golden and liquid evaporates.
05 - Sprinkle flour over vegetables and cook, stirring continuously, for 1 minute.
06 - Gradually pour in beef broth while stirring to combine. Add Worcestershire sauce, tomato paste, and Dijon mustard. Scrape browned bits from the skillet to incorporate fully.
07 - Allow sauce to simmer for 3 to 4 minutes until slightly thickened.
08 - Reduce heat and stir in sour cream until smooth, avoiding boiling. Return seared beef with juices to the skillet and warm through for 2 to 3 minutes.
09 - Plate egg noodles and top with beef stroganoff. Garnish with chopped parsley before serving.