Start by slicing the beef and chopping the onions and mushrooms to prepare all ingredients.

Heat olive oil in a large skillet over medium-high heat. Add the beef in batches and sear until browned, about 3 to 4 minutes per batch.

Remove the seared beef from the skillet and set aside. Add chopped onions and sliced mushrooms to the same skillet and cook until onions are soft and mushrooms are browned, about 5 to 6 minutes.

Add minced garlic and all-purpose flour to the skillet, stirring continuously for about 1 minute to cook out the flour taste.

Slowly pour in the beef broth, stirring constantly to avoid lumps, forming the base of the sauce.

Stir in Worcestershire sauce, Dijon mustard, salt, and pepper. Let the sauce simmer for about 5 minutes until it thickens slightly.

Reduce heat to low and stir in sour cream until the sauce is smooth and creamy.

Return the seared beef to the skillet, stirring to coat with the sauce, and cook for an additional 2 to 3 minutes until heated through.

Remove the skillet from heat and let the stroganoff rest for a few minutes before serving to allow the flavors to meld.