01 - Cook the egg noodles in a large pot of boiling salted water according to package instructions. Drain, toss with a little butter if desired, and set aside.
02 - In a bowl, toss the beef strips with flour, salt, and pepper until evenly coated.
03 - Heat 1 tablespoon of butter and the oil in a large skillet over medium-high heat. Add the beef in batches, searing quickly until browned on all sides (about 2 minutes per batch). Remove the beef and set aside.
04 - In the same skillet, add remaining butter. Sauté the onion for 2–3 minutes, then add the mushrooms and cook until softened and golden, about 5 minutes. Stir in the garlic and cook for 1 minute more.
05 - Add tomato paste and stir until well combined. Pour in beef broth, scraping up any browned bits. Bring to a gentle simmer and let reduce for 5 minutes.
06 - Lower the heat to medium-low. Stir in sour cream, Dijon mustard, and Worcestershire sauce. Mix until smooth and gently heated—do not boil.
07 - Return the seared beef and any juices to the skillet. Stir until just heated through and coated in the sauce. Taste and adjust seasoning with salt and pepper.
08 - Serve the beef stroganoff hot over the prepared egg noodles. Garnish with chopped parsley if desired.