In a small heavy skillet cook the bread crumbs, the horseradish, and the mustard with salt and pepper to taste in the butter over moderate heat, stirring, until the crumbs are golden brown and transfer the horseradish crumbs to a bowl. Wipe the skillet clean, in it heat the oil over moderately high heat until it is hot but not smoking, and in it saute the filets, patted dry and seasoned with salt and pepper, for 1 minute on each side. Reduce the heat to moderately low and cook the filets for 5 minutes more on each side for medium-rare meat. Transfer the filets to plates and pour off the fat from the skillet. In the skillet cook the onion over moderate heat, stirring, until it is golden, add the wine, and boil the mixture, scraping up the brown bits, until the liquid is reduced to a glaze. Spoon the onion mixture over the filets and top the filets with the horseradish crumbs. Serves 2. Gourmet November 1993