• Preheat the oven to 400℉, and make sure the oven rack is in the center.

Prepare The Mushroom Stuffing

• Heat 2 tablespoons of the olive oil in a large skillet over medium heat. Add the sliced leeks, mushrooms, and garlic and season with salt and pepper. Saute until the moisture from the mushrooms evaporates, about 8 minutes.
  3 tablespoon Olive oil, 1 large Leek, 12 oz Baby Portobello mushrooms, Salt, Black pepper, 2 cloves Garlic
• Add the spinach and the chopped fresh herbs. Continue cooking until the moisture from the spinach is wilted, about 2 minutes. Set aside while you prepare the beef tenderloin.
  2 cup Baby spinach, 2 teaspoon Thyme, 2 teaspoon Rosemary, 2 tablespoon Parsley

Stuff The Beef Tenderloin

• Placed the butterflied beef tenderloin between two sheets of plastic wrap and gently pound with the mallet to a ½ inch thickness. Brush the surface with the remaining 1 tablespoon of olive oil and season with salt and pepper.
  1½ lb Beef Tenderloin
• Stir the Parmesan cheese into the cooled vegetable mixture and spread evenly over the pounded beef tenderloin, leaving a ½ inch border along the sides.
  ¼ cup Parmesan cheese
• Carefully roll up the tenderloin like a jelly roll and secure with the butcher twine. Season the rolled up meat with salt and pepper and place in the center of the roasting pan on top of the sliced onions.
  1 large Onion
• Tuck the carrot chunks around the beef tenderloin in the roasting pan and pour the beef broth around the roast. Place in the oven to roast until an instant read thermometer reads 125 ℉- 130 ℉ for medium rare, or approximately 35 - 40 minutes.
  6 large Carrots, 1 cup Beef Broth
• Transfer the beef roast to a platter and cover loosely with aluminum foil to keep warm for about 10 - 15 minutes, keeping the vegetable warm in the turned off oven.

Make The Pan Juices

• To make the gravy, transfer the pan juices to a sauce pan and reduce over medium high heat. Add the butter and stir to emulsify and thicken the sauce.
  2 tablespoon Butter
• After letting the roast rest, carve the stuffed tenderloin and transfer the vegetables around the beef on the serving platter. Serve with the thickened pan juices.