Cook the noodles. Bring a pot of salted water to a boil and cook the egg noodles according to the package directions.
Drain them and set them aside.
Brown the beef. Heat a large skillet over medium heat. Add the ground beef and cook until browned, breaking it up with a spoon as it cooks. Drain off extra fat if needed.
Cook the vegetables. Add the butter, onion, and mushrooms to the skillet.
Cook for about 5 to 7 minutes, until the onion softens and the mushrooms release their moisture. Stir in the garlic and cook for 30 seconds.
Add the flour and seasoning. Sprinkle the flour over the beef mixture and stir well so everything gets coated. Add the salt, pepper, and paprika, then cook for about 1 minute.
Make the sauce. Slowly pour in the beef broth while stirring to keep the sauce smooth.
Add the Worcestershire sauce and Dijon mustard, then let the mixture simmer for 3 to 5 minutes until it thickens slightly.
Stir in the sour cream. Lower the heat and add the sour cream. Mix gently until the sauce turns creamy and smooth. Do not boil it after adding the sour cream, or it may separate.
Combine and serve. Add the cooked noodles to the skillet and toss them in the sauce, or serve the stroganoff over the noodles.
Finish with parsley if you want a fresh touch.