01 - Bring a large pot of salted water to a boil. Cook egg noodles according to package directions. Drain and toss with 1 tablespoon butter. Set aside.
02 - In a bowl, combine beef strips with flour, salt, and black pepper until evenly coated.
03 - Heat 1 tablespoon butter and olive oil in a large skillet over medium-high heat. Add beef in a single layer and sear 1 to 2 minutes per side until browned but not fully cooked. Remove beef and keep warm.
04 - Lower heat to medium. Add remaining 1 tablespoon butter to skillet. Sauté onions for 2 to 3 minutes until softened, then add garlic and cook 30 seconds.
05 - Add mushrooms and cook, stirring occasionally, until browned and liquid evaporates, about 5 to 7 minutes.
06 - Stir in beef broth, Worcestershire sauce, and Dijon mustard. Scrape browned bits from skillet. Simmer for 5 minutes to reduce slightly.
07 - Return beef and accumulated juices to skillet. Simmer gently for 2 to 3 minutes until beef is just cooked through.
08 - Reduce heat to low. Stir in sour cream and chopped parsley until smooth and warmed through without boiling. Adjust seasoning with salt and pepper to taste.
09 - Plate buttered egg noodles and spoon beef mixture over them. Garnish with additional parsley if desired.