Preheat a very large frying pan over medium high heat with olive oil. When the olive oil is hot but not smoking, add in the steak. Brown on one side for 2 minutes, flip, and brown on the other side for 2-3 minutes or until cooked to your preference.
Remove steak from the pan and place into a bowl.
In the same pan, add in the garlic, onion, and butter. Stir for 2 minutes or until the garlic and onions are softened and butter has melted.
Pour the butter over the steak and toss. Stir in fried parsley. Enjoy!