Cook the egg noodles according to package directions, then drain and set aside.

Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Season beef strips with salt and pepper, then sear in a single layer for 1–2 minutes per side until browned. Remove beef from the pan and set aside — don't overcook it here, it'll finish cooking in the sauce.

In the same skillet, add the remaining olive oil and butter over medium heat. Add the onions and cook for 3–4 minutes until softened.

Add the garlic and mushrooms, cooking for another 5 minutes until the mushrooms are golden and most of the moisture has cooked off.

Sprinkle the flour over the mushroom mixture and stir well to coat. Cook for 1 minute.

Pour in the beef broth, Worcestershire sauce, and Dijon mustard. Stir everything together and let it simmer for 5 minutes until slightly thickened.

Reduce heat to low. Stir in the sour cream until smooth and well incorporated. Add the beef back in and heat gently for 2–3 minutes — avoid boiling or the sour cream may curdle.

Taste and adjust seasoning. Serve over egg noodles and garnish with fresh parsley.