Method

1. Preheat the oven to 400°F.
2. To prepare the pesto: Blend 1 1/2 cups of arugula, the pine nuts, and horseradish in a food processor until the nuts are finely chopped.
3. Add the Parmesan cheese and slowly blend in the extra-virgin olive oil.
4. Season to taste with salt and pepper.
5. To prepare the crostini: Preheat the oven to 400°F.
6. Thinly slice the ciabatta crosswise into 24 ¼-inch-thick slices and arrange the slices in a single layer on two large baking sheets.
7. Drizzle with 2 tablespoons of olive oil and season with salt and pepper.
8. Toast in the oven for 5 minutes or until they are slightly golden.
9. Remove from the oven and cool.
10. Maintain the oven temperature.
11. Cut the filet lengthwise into 4 even pieces.
12. Place a large frying pan over high heat.
13. Sprinkle the beef filets with salt and pepper and drizzle the beef with the remaining 2 tablespoons of olive oil.
14. Place the beef and rosemary sprigs in the very hot pan and cook until the beef is brown on all sides but still rare in the center, about 6 minutes total.
15. Place the pan in the oven for 2 minutes.
16. Remove the beef from the oven and let rest in the pan for 5 minutes.
17. Discard the rosemary.
18. Stir the basil, chives, parsley, and tarragon on a shallow plate.
19. Roll the beef filets in the fresh herbs to coat.
20. Using a sharp knife, thinly slice the beef filets crosswise.
21. Arrange the remaining arugula leaves atop the crostini.
22. Top with the beef slices then drizzle the pesto over the beef and serve.