Sprinkle the steaks generously with salt on both sides. Press the top and bottoms of the steaks into the peppercorns to crust on each side.
Heat 2 tablespoons oil in a large heavy saute pan or cast-iron pan over medium-high heat until very hot. Add the steaks and sear for 3 to 4 minutes on each side. Cook until the internal temperature is around 125 degrees F for medium-rare. Remove the steaks from the pan and allow them to rest.
In the same pan the steaks were cooked in, add the shallots along with the remaining tablespoon oil and the green peppercorns and reduce the heat to medium. Cook until the shallots are softened and lightly browned, 2 to 3 minutes.
Turn off the heat, then add the brandy and return the heat to medium. Cook for 1 minute. Add the beef stock and cream, then reduce the liquid by half until thickened, 8 to 10 minutes. Season with salt as needed.
Turn off the heat. Swirl in the butter and melt, stirring often. Return the steaks to the pan and coat with the sauce. Sprinkle with the parsley and a splash of red wine vinegar to balance the richness of the sauce. Place the steaks on a plate, then spoon the sauce over and serve.