1. Heat a large skillet over medium-high. Add the olive oil and let it get hot. Add the sliced steak in a single layer and sear for about 1 minute per side, just until browned. Work in batches if needed to avoid overcrowding. Transfer the beef to a plate and keep warm.

2. Add the butter to the same skillet, then stir in the onion and mushrooms. Cook for 6–8 minutes, or until the vegetables are soft and lightly browned.

3. Add the garlic and cook for 1 minute. Sprinkle in the flour and stir another minute to coat the vegetables.

4. Pour in the beef broth, scraping up any browned bits. Stir in the heavy cream and let the mixture simmer for 1–2 minutes until slightly thickened.

5. In a small bowl, mix a few spoonfuls of the warm sauce into the sour cream to temper it. Add the sour cream mixture back into the skillet and stir well.

6. Add the Worcestershire sauce, Dijon mustard, salt, and pepper. Simmer until the sauce becomes creamy.

7. Return the beef and any accumulated juices to the skillet. Warm through without boiling.

8. Serve over cooked egg noodles and garnish with green onion or parsley.