01 - Bring a large pot of salted water to a rolling boil. Add the egg noodles and cook according to package directions until al dente. Drain thoroughly and set aside.
02 - While the noodles cook, heat olive oil in a large skillet over medium-high heat. Add the ground beef and cook, breaking it apart with a wooden spoon, until fully browned and no pink remains. 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. Stir in the sliced mushrooms and cook for an additional 5 minutes until golden brown. Add 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 smooth roux and cook off the raw flour taste.
05 - Gradually pour in the beef broth while whisking constantly to prevent lumps from forming. Stir in the Worcestershire sauce and Dijon mustard. Bring the mixture to a gentle simmer and cook for 5 minutes until the sauce has slightly thickened.
06 - Return the browned beef to the skillet and stir to combine. Reduce the heat to low and gently fold in the sour cream until fully incorporated. Season with salt and black pepper to taste.
07 - Add the cooked egg noodles to the skillet and toss gently until evenly coated with the creamy sauce. Serve immediately, garnished with fresh chopped parsley if desired.