01 - Season beef strips with salt and pepper, then toss evenly with flour.
02 - Heat 1 tbsp butter and olive oil in a large skillet over medium-high heat. Add beef in batches, searing until browned, about 1-2 minutes per side. Remove and set aside.
03 - Add remaining butter to skillet. Sauté onions until translucent, about 3 minutes. Add mushrooms and cook until softened and golden, 5-7 minutes.
04 - Stir in garlic and tomato paste; cook for 1 minute until fragrant.
05 - Pour in beef broth, scraping up browned bits. Simmer for 3-4 minutes to reduce slightly.
06 - Lower heat and mix in sour cream, Dijon mustard, and Worcestershire sauce until smooth. Return beef and juices to skillet and gently simmer 2-3 minutes without boiling. Adjust seasoning with salt and pepper.
07 - Prepare egg noodles according to package instructions. Drain thoroughly.
08 - Plate stroganoff over noodles and garnish with chopped parsley if desired.