01 - Cook the egg noodles in a large pot of boiling salted water according to package directions. Drain well, toss with a small amount of butter if desired, and set aside.
02 - In a mixing bowl, combine beef strips with flour, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Toss until evenly coated.
03 - Heat 1 tablespoon butter and vegetable oil in a large skillet over medium-high heat. Add beef in small batches, searing quickly until browned on all sides, approximately 2 minutes per batch. Remove browned beef and set aside.
04 - Add remaining butter to the same skillet. Sauté onion for 2 to 3 minutes until translucent. Add mushrooms and cook until softened and golden brown, about 5 minutes. Stir in garlic and cook for 1 additional minute.
05 - Add tomato paste to the skillet and stir until thoroughly combined. Pour in beef broth while scraping up any browned bits from the bottom. Bring to a gentle simmer and reduce for 5 minutes.
06 - Reduce heat to medium-low. Stir in sour cream, Dijon mustard, and Worcestershire sauce. Mix until smooth and heated through—avoid boiling to prevent curdling.
07 - Return seared beef and accumulated juices to the skillet. Stir until just heated through and evenly coated with sauce. Season with salt and pepper to taste.
08 - Serve the beef stroganoff immediately over prepared egg noodles. Sprinkle with chopped fresh parsley if desired.