Rinse and Pat the steak dry with a paper towel and season both sides with salt and pepper. Heat a large skillet until smoking slightly, then add oil, followed by the steak.
Press down with tongs, and cook for 2 minutes on the first side and 1 minute on the second side or until medium-rare. Thicker steaks take longer.
Plate the steak, then throw in green beans, mushrooms, and/or onions and toss in the fat, cooking for about 2 minutes. Plate alongside the resting steak.
In a separate small saucepan, add lime juice, fish sauce, brown sugar, and butter. Stir until the butter is incorporated. Pour the sauce over the steak and veggies and serve with the remaining lime wedges. Enjoy with a glass of red wine.
Note: Lemon can be substituted for the lime.