Begin by patting the beef sirloin cubes dry with paper towels to remove excess moisture.

In a mixing bowl, combine the all-purpose flour, salt, black pepper, garlic powder, and onion powder. Whisk until well blended.

Take the dry beef cubes and dredge them in the flour mixture, ensuring each piece is entirely coated.

Place a large skillet over medium-high heat and add 2 tablespoons of unsalted butter.

Carefully add the coated beef cubes to the skillet in batches, sear each side for about 2-3 minutes.

Lower the heat and add the remaining butter to the skillet. Scrape up any browned bits for extra flavor.

Once the butter has melted, add the minced garlic and sauté for about 30 seconds until fragrant.

Stir in chopped fresh parsley, dry sherry, Worcestershire sauce, soy sauce, Dijon mustard, and dried thyme. Cook for 1 minute.

Pour in the beef broth to deglaze the skillet, simmer for 2-3 minutes until slightly thickened.

Return the seared beef cubes to the skillet and gently stir to coat them well with the sauce.

Continue simmering until the beef reaches the desired doneness, ideally around 145°F (63°C) for medium-rare.

Once done, remove from heat and serve immediately, sprinkling extra fresh parsley on top.