Season the steaks with salt and pepper. Coat with the flour and shake off any excess.
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.
Lower the heat and return the steaks to the pan along with any juices, turning them in the sauce. Transfer the steaks and sauce to plates and serve with the shoestring potatoes.