1. Preheat oven to 450 degree F and arrange rack in upper third; lightly brush a shallow baking pan with oil. Rinse beef and pat dry. Heat oil in a large skillet over moderately high heat until hot but not smoking. Add beef and brown on all sides, turning, about 8 minutes. Transfer to prepared pan. Let stand 10 minutes.
2. Meanwhile, whisk together salt, rosemary, crushed peppercorns, and flour. Add egg whites and 1/2 cup plus 2 tablespoons water; stir until it is the consistency of a paste. Pat onto top and sides of beef (not bottom), coating completely.
3. Roast until an instant-read thermometer inserted in center by 2 inches register 125 degree F for medium-rare, about 30 minutes. Remove from oven and let stand 5 minutes.
4. Present beef on a large grooved cutting board garnished with bay leaves and whole peppercorns, if desired (note: whole bay leaves are not edible); let stand 10 minutes.
5. Chip off crust (discard) and cut beef into 1/4-inch-thick slices; arrange on a serving platter. Spoon some sauce over slices and top with reserved mushrooms. Serve remaining sauce in a gravy boat on the side. Makes 8 servings.