Pat the beef dry and slice it into thin, even pieces. Season with salt, black pepper, paprika, and garlic powder.
Heat olive oil in a large skillet over medium-high heat. Sear the beef for about 2–3 minutes per side, working in batches if necessary. Transfer to a clean plate.
Reduce the heat to medium and add the butter. Cook the onion and mushrooms for about 5–7 minutes, until softened and lightly golden.
Add the minced garlic and cook for about 30 seconds.
Sprinkle the flour over the vegetables and stir for about 1 minute.
Slowly add the beef broth while stirring. Add Worcestershire sauce, Dijon mustard, and Italian seasoning.
Simmer the sauce gently for 3–5 minutes, until it begins to thicken.
Reduce the heat to low and stir in the sour cream and heavy cream. Do not let the sauce boil.
Return the browned beef and its juices to the skillet. Simmer gently for another 2–3 minutes, or until the beef is cooked through.
Meanwhile, cook the egg noodles according to package directions. Drain well.
Serve the creamy beef stroganoff over the warm egg noodles and garnish with fresh parsley.