This recipe is simplicity at its best.
In my opinion pork tenderloin is one of the nicest and most versatile pieces of meat to cook. It's very lean and yet when cooked with just a little bit of care it is very moist.
Pork tenderloins come in a variety of sizes, with the most common being around a pound. If the pork tenderloin we purchase is a pound or more, we cut it in half and end up with enough meat for two meals.
Most pork tenderloins will come from your butcher with some silver skin still left on (I have no idea why butchers don't remove it). Silver skin is a very thin layer of silvery connective tissue that will not melt or brown during the cooking process. It needs to be removed. Using the tip of a sharp knife, slide it under the silver skin and slide the knife towards one end of the tissue and then reverse the knife and slide it towards the other end of the tissue.
The cooking method is called a "reverse sear". I didn't invent the cooking method, I have no idea who did. A lot of recipes call for meat to be browned (seared) on the outside before putting it the oven. With a reverse sear you cook the meat in the oven and get to the desired doneness first. Then you sear it in a skillet.
The picture shows the pork tenderloin served on a bed of buttered parsnips.