Directions

1. To make the creamy mustard sauce, whisk together sour cream, Dijon, horseradish and chives; season with salt and pepper, to taste. Set aside.
2. Preheat oven to 500 degrees F.
3. In a small bowl, combine vegetable oil, thyme and garlic.
4. Let tenderloin stand at room temperature 1 hour. Using paper towels, pat tenderloin dry. Drizzle with vegetable oil mixture; season with salt and pepper, gently pressing to adhere.
5. Place tenderloin on a rack in a shallow roasting pan. Place into oven and roast for 15 minutes.
6. Reduce oven temperature to 375 degrees F. Continue roasting until it reaches an internal temperature of 130-135 degrees F for medium-rare, about 15-25 minutes, or until desired doneness. Let rest 10 minutes before slicing.
7. Serve immediately with creamy mustard sauce.