Score steak diagonally across grain at 3/4-inch intervals.
Whisk together vinaigrette, mustard, and, if desired, anchovy paste. Pour 1/2 cup mixture in a shallow dish or heavy-duty zip-top plastic bag; reserve remaining mixture. Add flank steak to dish or bag, cover or seal, and chill 1 hour, turning occasionally.
Cook potato in boiling water to cover in a large saucepan 10 to 12 minutes or until tender; drain and toss with 1/2 cup reserved vinaigrette mixture. Set aside.
Cook green beans in boiling water to cover 3 to 4 minutes or until crisp-tender; drain. Plunge beans into ice water to stop the cooking process; drain. Pat dry with paper towels, and set aside.
Remove flank steak from marinade, and discard marinade.
Grill steak, covered with grill lid, over medium-high heat (350° to 400°) 5 minutes on each side or to desired degree of doneness. Remove from grill, and let stand 10 minutes. Cut diagonally across grain into 1/4-inch-thick slices.
Toss salad greens with 1/4 cup remaining vinaigrette mixture, and place on 4 serving plates. Arrange steak, green beans, potato, tomato, olives, and egg on salad greens. Drizzle with remaining vinaigrette mixture, and serve immediately.