01 - Heat olive oil in a large pot or deep skillet over medium-high heat. Add the beef slices, season with salt and pepper, and sear until browned. Remove and set aside.
02 - In the same pot, add diced onion and cook for 2–3 minutes until softened. Add garlic and mushrooms; cook for another 4–5 minutes until mushrooms are tender.
03 - Pour in beef broth, Worcestershire sauce, and Dijon mustard. Stir to combine, scraping up any browned bits from the bottom.
04 - Bring to a boil, then add the egg noodles. Stir well. Cover and reduce heat to simmer; cook for about 8–10 minutes, stirring occasionally, until noodles are tender.
05 - Return the beef to the pot. Stir in sour cream and cream cheese, if using, until the sauce is creamy and heated through.
06 - Taste and adjust seasoning with salt and pepper.
07 - Garnish with chopped parsley and serve hot.