In an oven-proof pan heat oil and butter over moderately high heat. Sear pork in pan turning to brown all sides, about 6 minutes total. Pour off fat. Set aside.
Combine all sauce ingredients in a large measuring cup and puree with a hand blender. Pour sauce over pork in the pan. Bring to a boil over medium high heat on the stove.
Cover pan with foil and transfer to oven. Cook 25-30 minutes until internal temperature measured with an instant-read thermometer is 145°F.
Remove from oven and let meat rest, covered, for 10 minutes.
Cut tenderloin into thick slices and serve with sauce.
Notes
If you want to experience new flavour combinations you need to buy new ingredients. Not everyone has Sherry vinegar and five spice powder in their pantry but you can easily find them both.