In a bowl, combine soy sauce, Worcestershire sauce, minced garlic, black pepper, onion powder, and a sprinkle of salt. Whisk together until well mixed.

Place your beef sirloin strips in a shallow dish and pour the marinade over them. Allow to marinate for at least 15 minutes at room temperature.

Preheat a large skillet over medium-high heat, adding a splash of olive oil. Allow until shimmering, about 2-3 minutes.

Carefully add the marinated beef to the skillet in batches. Sear for 3-4 minutes per side until golden-brown.

Reduce heat to medium-low and add unsalted butter to the skillet. Stir into beef for about 1-2 minutes until coated.

Sprinkle freshly chopped parsley over the dish and gently stir to combine.

Transfer Butter Beef onto a serving platter and serve immediately with sides of your choice.