Porcini Rubbed Roast Beef with Root Vegetable Puree

Preheat oven to 325 degrees F. Trim fat from beef. Combine mushroom powder, 1 teaspoon kosher salt, the rosemary, and 1/2 teaspoon ground pepper in a small bowl. Sprinkle the herb mixture evenly over all sides of the meat; rub in with your fingers.

Place the meat on a rack in a shallow roasting pan. Insert an oven-going meat thermometer into the center of the roast. If using eye of round roast, roast, uncovered, for 1 1 1/2 to 1 3/4 hours or until the thermometer registers 135 degrees F (it is not recommended to roast an eye of round roast past medium-rare doneness). If using beef tenderloin roast, increase the oven temperature to 425 degrees F. Roast, uncovered, for 35 to 45 minutes or until thermometer registers 135 degrees F (medium-rare) or 45 to 50 minutes or until the thermometer registers 150 degrees F (medium).

Meanwhile, prepare vegetable puree: Cook potatoes and rutabaga in a large covered saucepan in enough boiling water to cover about 20 minutes or until the vegetables are tender; drain.

Mash the potatoes and rutabaga with a potato masher or beat with an electric mixer on low speed. Add butter, the remaining 1/4 teaspoon each of kosher salt and ground pepper. Gradually beat in enough milk to make the mixture light and fluffy. Cover and keep warm.

Cover the meat with foil and let stand for 15 minutes before slicing.

Meanwhile, prepare sauce: Coat a medium skillet with cooking spray; heat the skillet over medium heat. Add shallot. Cook for 3 to 5 minutes or until tender, stirring occasionally. If desired, add Marsala wine; cook, uncovered, over medium heat for 3 to 5 minutes or until the wine is nearly evaporated. Add beef broth and crushed mushrooms. Bring to boiling; reduce heat. Simmer, uncovered, for 2 minutes. Combine half-and-half and cornstarch in a small bowl until smooth. Add to the mushroom sauce. Cook and stir until slightly thick and bubbly; cook and stir for 2 minutes more. Cover and keep warm.

Thinly slice the meat to serve. Spoon sauce over the meat. Serve with the reserved vegetable puree, stirring the spinach into the puree just before serving.