Prep Time: 10 Minutes
Cook Time: 35 Minutes
Total Time: 45 Minutes
1. Heat oven to 350ºF.
2. Heat butter and oil in heavy skillet over medium-high heat.
3. Pat tenderloin dry with paper towel. Season with salt and pepper and rosemary. Sear in skillet until browned on all sides. Remove from skillet, keep warm.
4. Add leeks to skillet. Cook, stirring occasionally for 5 minutes, until wilted. Deglaze pan with white wine, scraping up any browned bits from the skillet. Turn heat off and stir in sour cream.
5. Nestle tenderloin into leeks. Place skillet into oven and roast 20 minutes (cook to 140ºF to 145ºF internal temperature, using thermometer to check temp).
6. Let rest 5 minutes before slicing. Serve, topping each serving with about ½ cup leeks from skillet.