Spinach and Mushroom-Stuffed Beef Tenderloin with Truffled Wine Sauce

For a light and elegant meal, serve your family and friends a beef tenderloin stuffed with spinach and mushrooms, with a truffle wine sauce. Our secrets to making the best beef tenderloin: Cook fast, keep it moist, and use a reliable thermometer. Remove the tenderloin from the oven when it is heated to 125 degrees, and the residual heat will bring it to perfection.
Preheat a large skillet over medium-high heat. Add 1 tablespoon of olive oil to the skillet; stir to coat. Add the bacon; cook for 2 minutes, stirring occasionally. Add the shallots; cook for 2 minutes, stirring occasionally. Add the mushrooms; cook for 3 minutes, stirring occasionally. Increase the heat to medium-high. Add garlic; simmer for 30 seconds. Pour in 1/2 cup beef stock; cook until the liquid has almost evaporated, stirring occasionally (about 8 minutes). Add the spinach; cook for 1 minute or until the spinach wilts.Preheat the oven to 350 degrees.With a sharp knife, cut the beef tenderloin horizontally in the center, but not through, on the other side; open flat, like a book. Place the beef between 2 sheets of plastic wrap; beat to an even 1/2-inch thickness (about 13 square inches) using a meat grinder or small heavy skillet. Brush beef with 1 1/2 teaspoons olive oil; sprinkle with 3/4 teaspoon salt and 1/2 teaspoon pepper. Spread the mushroom mixture evenly over the beef, leaving a 1/2-inch thick rim around the edges. Roll the beef into a jelly roll. Secure with twine at 2-inch intervals. Brush beef evenly on all sides with the remaining 1 tablespoon olive oil; sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper.Place the beef on a jelly roll tin. Bake at 350 ° C for 30 minutes. Increase the oven temperature to 450 ° (do not remove the beef from the oven); bake for another 25 minutes or until the thermometer reads 125 °. Let stand for 15 minutes; cut across the fibers into 12 slices.Combine the remaining 2 1/2 cups beef stock, wine, and thyme and bring to a boil. Cook until reduced to 1 cup (about 25 minutes). Discard the thyme sprigs. Combine 1/4 cup stock mixture and flour in a small bowl, stirring with a whisk until smooth. Add the flour mixture to the stock mixture. Bring to a boil; cook for 1 minute, stirring occasionally. Remove from the heat and add the remaining 1/4 teaspoon salt, remaining 1/4 teaspoon pepper, butter and truffle oil. Serve the sauce with the beef.