Take the beef steaks out of the refrigerator and let them come to room temperature for about 30 minutes. Pat the steaks dry with paper towels and season both sides generously with salt and black pepper.

In a large skillet over medium-high heat, add 2 tablespoons of butter. Once melted and bubbling, add the steaks. Cook for about 4-5 minutes on each side for medium-rare, or until your preferred doneness is achieved. Use a meat thermometer to check the internal temperature (130°F for medium-rare). Once cooked, remove the steaks from the skillet and let them rest on a plate, loosely covered with foil.

In the same skillet, add the remaining 2 tablespoons of butter. Add the sliced onions and cook over medium heat until they are soft and golden brown, about 8-10 minutes. Stir in the minced garlic and cook for an additional minute until fragrant.

Sprinkle the flour over the onions and stir well to combine. Cook for another minute to eliminate the raw flour taste. Gradually pour in the beef broth while stirring to prevent lumps. Add the Worcestershire sauce and bring the mixture to a simmer. Let the gravy simmer for about 5-7 minutes until it thickens. Season with salt and pepper to taste.

Slice the rested steaks against the grain and plate them. Spoon the onion gravy generously over the steak. Garnish with chopped fresh parsley before serving.