Longhorn Steakhouse's Portabella Beef Tenderloin

Portabella Cream Sauce:

• 1 tablespoon butter
• 2 cups sliced baby portabella mushrooms
• 1/2 cup chives
• 1/4 cup white wine
• 1 cup heavy cream
• 1 teaspoon garlic powder
• 2 teaspoons soy sauce
• Pinch of cayenne pepper
• 1/4 teaspoon each kosher salt & black pepper

Herb Rub:

• 2 tablespoons fresh rosemary-finely chopped
• 2 tablespoons fresh thyme-finely chopped
• 1 tablespoon kosher salt
• 2 teaspoons ground black pepper
• 1 teaspoon onion powder
• 1 teaspoon garlic powder
• 1 whole beef tenderloin, 4-6 pounds, trimmed and skinned
• Olive Oil

Mix rub ingredients and set aside. Lay out the tenderloin, smoothest side up. Fold the tail end of the tenderloin under to make the thickness uniform. Tie the tenderloin snugly with butcher's twine at 2-inch intervals and secure the folded end with two strings. Lightly coat with oil. Season all over with the herb rub.
Sear the tenderloin over a hot grill (450 degrees) for about 20 minutes, turning a quarter turn once every 4-5 minutes. Then slide the roast over to a less warm side of the grill (250 degrees), loosely cover it with foil and cook until it reaches your desired doneness, 20 to 30 minutes for medium rare (125° to 130°F), turning once. Remove from the grill, loosely tent with foil, and let rest for 10 minutes (important!).
Snip and remove all the twine from the roast. Cut the meat crosswise into 1/2- to 1-inch slices and arrange onto a serving platter. Garnish with fresh rosemary sprigs and serve warm.