Preheat oven to 375ºF
After removing the silver skin, slice the tenderloin lengthwise making sure to not go all the way through. If there’s a tail, do the same with it. Make a few slits into the meat which will help when pounding it down.
Place a cling film on top and flatten it down to about ¼-inch thick with a meat mallet; discard the plastic wrap.
Spoon the stuffing in the middle and spread evenly, leaving a 1 ½-inch space from the edges.
Starting from the long side, tightly roll the tenderloin, tucking in the ends, until the pork is nicely rolled.
Using kitchen twine, tie a loop on one end, make a firm knot to hold without cutting into the flesh; leave a 2-inch long string end for later.
Go round and round keeping the string about 1-inch apart to the other end. Crisscross the twine and do the same in the other direction to the starting point. Tie a knot with the 2-inch string from the starting point and the loose end of the string.
If the ends didn’t tuck in well, secure them with toothpicks. Generously season the stuffed pork on all sides with sea salt and freshly ground black pepper.
In an ovenproof saucepan over medium-high heat, add oil. When hot and shimmering, add tenderloin and quickly sear on one side only, about 1 ½ minutes.
When nicely brown, flip it over and transfer to the preheated oven. Cook for 20 minutes or until the internal temperature reaches 140 - 145ºF.
Remove from the heat and transfer the tenderloin to a cutting board to rest before slicing, covering loosely with foil.