Remove tenderloin from the refrigerator 1 hour before roasting. It has to be at room temperature. Wash and pat dry tenderloin.
5-6 pounds beef tenderloin
Preheat the oven to 395°F and prepare a baking tray in the middle of the oven.
Season beef tenderloin with salt and pepper. Rub with butter, Dijon mustard and thyme.
1 Tablespoon coarse kosher salt, ½ Tablespoon black pepper, 3 Tablespoons salted butter, 2 Tablespoons Dijon mustard, 1 Tablespoon dried thyme
Heat a non-stick skillet over high heat with oil. Oil must be smoked hot to sear the tenderloin. Sear all 4 sides until browned.
1 teaspoon extra virgin olive oil
Transfer tenderloin without pan juices in a large enough baking dish.
In the same non-stick skillet, cook mushrooms until half tender. Transfer mushrooms around beef tenderloin in the baking dish with the pan juices.
8 ounces brown mushrooms
Cook in the oven for about 25 minutes or to your favorite doneness of roast. For medium rare, an instant-read thermometer inserted in the roast must register 120 - 125°F.
Remove roast and let rest for about 15 minutes before slicing.
Serve with the cream sauce.