Cook the Egg Noodles: Bring a medium pot of salted water to a boil. Cook the egg noodles according to package instructions until al dente. Drain and set aside.

Cook the Beef: Heat olive oil in a large skillet over medium-high heat. Season the beef strips with salt and pepper. Add them to the skillet and cook for 1-2 minutes per side until browned. Remove from the skillet and set aside.

Sauté the Vegetables: In the same skillet, melt the butter over medium heat. Add the sliced mushrooms and onion, cooking until softened (about 5 minutes). Add minced garlic and cook for an additional 30 seconds.

Make the Sauce: Stir in the beef broth, Dijon mustard, and Worcestershire sauce. Simmer for 2-3 minutes to reduce slightly.

Add the Sour Cream: Lower the heat and stir in the sour cream until the sauce is smooth and creamy. Return the beef to the skillet and toss to coat in the sauce. Cook for 1-2 more minutes to heat through.

Combine and Serve: Plate the cooked egg noodles and spoon the beef and sauce mixture over the top. Garnish with chopped parsley, if desired.