In a large skillet, heat olive oil over medium-high heat. Add the thinly sliced beef and season with salt and pepper. Brown the beef for about 3-4 minutes, stirring occasionally. Remove the beef from the skillet and set aside.

In the same skillet, add the diced onion and cook for 2-3 minutes until translucent. Then add the sliced mushrooms and cook until they are tender, about 5 minutes. Stir in the minced garlic and cook for an additional minute.

Pour in the beef broth, Worcestershire sauce, and Dijon mustard, stirring to combine. Bring the mixture to a simmer and cook for about 5 minutes, allowing the flavors to meld.

Lower the heat and stir in the sour cream until well combined. Return the beef to the skillet and heat through for another 2-3 minutes. Adjust seasoning with salt and pepper.

Meanwhile, toast the French bread slices on a pan or in a preheated oven until golden brown.

To serve, place a slice of toasted French bread on each plate and top with the beef stroganoff mixture. Garnish with chopped parsley.

If a lighter version is desired, consider replacing sour cream with Greek yogurt.

For added depth of flavor, you may include a splash of white wine to the broth.