1. Put a large sheet of plastic film on a countertop or similar.
2. Sprinkle the plastic film with your favorites spices (i.e. thyme, black pepper and rosemary).
3. Place tenderloins on top of the film and wrap them.
4. Put them into the fridge for 30 min.
5. While the pork is marinating wash 4 medium size potatoes and dry. Don't peel the potatoes.
6. Slice down the potatoes taking care not to cut all the way through.
7. In a bowl mix 4 tablespoon of extra virgin olive oil, 1/2 teaspoon of salt with some thyme, rosemary, ground black pepper and chopped fresh parsley.
8. Preheat oven to 400ºF (200º C).
9. When warm brush the potatoes with the mixture making sure it gets in between every slice.
10. Bake for 15 minutes.
11. While potatoes are baking put a layer of coarse (kosher) salt in a large baking plate.
12. Place tenderloins on top of the salt layer.
13. Cover tenderloins with enough coarse salt to make sure both tenderloins are fully covered.
14. Brush again the potatoes with the mixture of olive oil and spices.
15. Bake at 400ºF (200ºC) both tenderloins and potatoes for 28-30 minutes. If possible, use separate baking plates for potatoes and pork but if you are using the same just make sure that the potatoes don't touch the coarse salt.
16. After 28-30 minutes you should see that the top layer of salt is starting to crack and that's the moment to remove from the oven to have a super juicy pork tenderloin (around 28 min for medium rare and 30 min for medium). In case you like it well done give it 2-3 more minutes.
17. Remove potatoes from the oven (they should have been around 45 min baking, first 15 min without the pork and then almost half an hour with the pork).
18. With a knife and a spatula or spoon crack open the salt crust making sure that is fully clean before eating. Otherwise it could be a too salty.
19. Transfer tenderloins and potatoes to a dish and brush off the remaining salt.
20. Slice tenderloins 1/2 inch thick and server with the Hasselback potatoes. Enjoy your Spanish pork recipes [1].