1. Heat the butter in a saute pan.
2. Season the tournedos, place in the pan and fry to the required degree and to a golden brown on both sides.
3. Remove the strings from the tournedos and place on the croutons on an oval dish.
4. Drain the fat from the pan, add the Madeira and reduce by half, add the sauce, reheat, correct the consistency and season. Pass through a fine strainer, reheat and add knobs of butter off the heat.
5. Place a sauted slice of foie gras and a thin slice of truffle on each tournedos, mask with the sauce and serve.