01 - Bring a large pot of salted water to a boil. Cook egg noodles according to package instructions until al dente. Drain, toss with a little butter if desired, and set aside.
02 - Pat beef strips dry with paper towels and season generously with salt and pepper.
03 - In a large skillet over medium-high heat, heat 1 tbsp olive oil and 1 tbsp butter. Add beef in batches, searing quickly for 1-2 minutes per side until browned but not fully cooked. Remove to a plate and set aside.
04 - In the same skillet, add 2 tbsp butter. Sauté onions for 2 minutes until softened. Add mushrooms and cook for 5-6 minutes, stirring often, until golden and most liquid has evaporated. Add garlic and cook for 30 seconds.
05 - Sprinkle flour over mushrooms and stir to coat evenly. Gradually pour in beef broth while stirring, scraping up any browned bits from the bottom. Add Worcestershire sauce and Dijon mustard. Simmer for 3-4 minutes until the sauce thickens slightly.
06 - Reduce heat to low. Stir in sour cream until smooth, taking care not to boil the mixture. Return beef and any accumulated juices to the skillet. Simmer gently for 2-3 minutes until beef is just cooked through and sauce is creamy. Adjust seasoning with salt and pepper.
07 - Serve beef stroganoff over warm egg noodles. Garnish with chopped parsley.