01 - Bring a large pot of salted water to a rolling boil. Add egg noodles and cook according to package directions until tender. Drain thoroughly and set aside.
02 - While the noodles cook, heat olive oil in a large skillet over medium-high heat. Add ground beef and cook until fully browned, breaking it apart with a wooden spoon. Transfer the beef to a plate using a slotted spoon and set aside.
03 - In the same skillet, add the diced onion and cook for 3 to 4 minutes until softened. Add the sliced mushrooms and cook for an additional 5 minutes until golden brown. Stir in the minced garlic and sauté for 1 minute until fragrant.
04 - Add the butter to the skillet and allow it to melt completely. Sprinkle in the flour and stir continuously for 1 to 2 minutes to form a light roux.
05 - Gradually pour in the beef broth while stirring constantly to prevent lumps from forming. Stir in the Worcestershire sauce and Dijon mustard. Bring the mixture to a simmer and cook for 5 minutes until the sauce thickens slightly.
06 - Return the browned beef to the skillet. Reduce the heat to low and gently stir in the sour cream until fully incorporated. Season with salt and black pepper to taste.
07 - Add the cooked egg noodles to the sauce and toss gently until evenly coated. Serve hot, garnished with fresh chopped parsley if desired.