In a large, heavy skillet, heat the olive oil over medium heat until rippling. Add the steaks and cook, turning once, 10 to 12 minutes total for medium-rare. Transfer to a plate. Add the shallots to the skillet and cook, stirring, until slightly softened, about 2 minutes. Add the green peppercorns and stir for 1 minute. Remove the pan from the heat and pour in the cognac; return to the heat and cook until nearly dry, about 1 minute. Pour in the beef broth, heavy cream and steak sauce; bring to a boil and cook, stirring, until reduced by half, about 5 minutes.