- 5- to 6-pound beef tenderloin, cleaned and silver skin removed
- 10 shallots, peeled and thinly sliced
- ½ cup canola oil
- 4 tablespoons fresh rosemary leaves, roughly chopped
- 4 tablespoons fresh thyme leaves, roughly chopped
- 8 garlic cloves, thinly sliced
- Sea salt and freshly ground black pepper, to taste
- 5 sprigs fresh rosemary
- Watercress Sauce (opposite)
- 2½ cups watercress, large stems removed (about 2 bunches)
- ½ cup Creme Fraiche or sour cream
- ½ cup Fresh Mayonnaise, or good-quality prepared mayonnaise
- ½ teaspoon sea salt
- Freshly ground black pepper, to taste
- To Make the Beef:
- Place the beef in a shallow dish and cover with the shallots, oil, rosemary, thyme, and garlic. Cover in plastic wrap, refrigerate, and marinate the meat overnight.
- Remove the filet from the refrigerator and allow it to come to room temperature, about 1 hour. Remove any remaining garlic, shallots, and herbs from the meat. Season with salt and pepper on all sides.
- Tuck the tip end under to make a uniformly thick piece of meat and tie the roast crosswise with kitchen twine every 2 inches, inserting the rosemary sprigs under the twine.
- Prepare a medium-hot grill.
- Grill the meat uncovered, turning a few times, until an instant-read thermometer reads 125°F. for medium rare, about 35 to 40 minutes.
- Transfer the filet to a carving board and let it rest for 15 to 20 minutes. If you plan to serve the meat cold, wrap it in plastic and refrigerate.
- When ready to serve, carve in ½-inch slices and serve with Watercress Sauce on the side.
- To Make the Watercress Sauce:
- In a blender or food processor, pulse the watercress until finely chopped. Add the crème fraîche, mayonnaise, salt, and pepper and process until smooth.
- Transfer to a bowl or plastic container and refrigerate until ready to use. It will keep for up to 5 days.