Bring the beef stock, cream and coffee beans to the boil, reduce the heat, simmer for approx. 5 mins. Strain, pour back into the same pan, allow to cool slightly. Add the chocolate and cognac and melt over a low heat. Add the butter gradually, stirring constantly. Return the pan to the hob a few times to barely warm the sauce; it must not boil. Season with salt and pepper.
Heat the clarified butter in a frying pan, fry the steaks for approx. 3 mins. on each side. Place them on a plate, cover and leave the meat to stand for approx. 5 min. Serve with the sauce.