1. Preheat oven to 400 degrees. Mince the garlic and parsley and set aside for later.
2. Divide flank steak into 4 equal portions, pat dry and season with kosher salt and freshly ground black pepper.
3. Heat a large cast iron pan over medium high heat until pan is very hot. Add oil and then 1 tablespoon of butter to pan and let melt. Sear steaks on both sides, about 3 minutes per side. Place cast iron skillet into oven and cook for an additional 3 minutes, or until steaks reach 125° on an instant read thermometer.
4. Carefully remove cast iron skillet from the oven and return to stovetop. Remove steaks from pan and set aside to rest while you prepare the pan sauce.
5. Heat the same skillet over medium low heat and add 1 tablespoon of butter. Add the garlic to skillet and sauté for 1-2 minutes. Add white wine and any juices from the resting steak to the pan and increase heat to medium high. Bring to boil and let reduce about 5 minutes until slightly thickened, scraping up brown bits from pan as it reduces.
6. Remove the pan from heat and add the final tablespoon of butter and freshly chopped parsley to sauce. Season with additional salt and pepper to taste. Slice flank steak against the grain, spoon sauce over the steak and serve.

Enjoy!