Start by patting the beef sirloin cubes dry with paper towels; this ensures optimal browning. Cut the beef into bite-sized pieces if not already done.

In a mixing bowl, combine all-purpose flour, salt, black pepper, garlic powder, and onion powder. Toss the beef cubes in this mixture until well coated.

Heat a large skillet over medium-high heat and add 2 tablespoons of unsalted butter. Once melted, add one-third of the beef cubes and sear for 3-4 minutes per side.

Repeat the searing process with the remaining beef in batches, adding more butter as needed to maintain richness.

Using the same skillet, reduce heat to medium and add the remaining butter. Once melted, add minced garlic and sauté for 30 seconds.

Stir in parsley, dry sherry, Worcestershire sauce, soy sauce, Dijon mustard, and dried thyme to the skillet.

Pour in beef broth, stirring well to deglaze the pan and allow the mixture to simmer for 5 minutes to thicken.

Return the sautéed beef to the skillet, coating each piece thoroughly in the sauce and let it simmer for 5-7 minutes.

Once heated through, serve the Garlic Butter Beef Bites over rice, mashed potatoes, or pasta, garnished with parsley.