Ideally the day before or the morning you are planning on cooking. If you do not have time, this can all be done at the time you are planning on cooking.
Rinse and dry the pork tenderloins. Generously, season with salt and pepper.
In a small bowl, combine the olive oil, garlic, and thyme.
Lay one piece of tenderloin on a board and using a spoon drizzle the oil, garlic and thyme mixture trying to keep the mixture in the center of the piece of meat.
Top the bottom tenderloin with the other tenderloin, trying to keep the garlic inside the two pieces. Using butcher twine, tightly tie the two pieces of meat together. Place in a dish and drizzle the remaining olive oil and garlic mixture over the meat and place in the refrigerator 8hours or overnight.