Preheat oven to 375F, rack in the middle
Heat a cast-iron or heavy oven-safe skillet over medium-high heat and add in 3 tablespoon of butter.
Once the butter begins to foam place the tenderloin in the pan and do not move for 4-6 minutes. You want it to create a sear (lightly brown).
Flip and sear other side for another 4-6 minutes.
Shut the heat off of the burner and immediately place 3 more tablespoon of butter in the pan.
Place the pan in the oven, continuing to cook until the internal temperature reaches 150°F, roughly 15-23 minutes. Again the cooking time will vary depending on how big your pork tenderloin is. Mine were 2 weighing around 1.5 lbs each so it was done in about 12-14 minutes.
Remove the pan from the oven and place on the burner.
Transfer the tenderloins to a plate and cover with foil to rest and prevent the juices from escaping.
Turn the burner to medium.
Add the remaining butter and bourbon.
Stir until the liquid has begun to reduce (about 2-3 minutes) and add in the honey to thicken.
Add in the salt, pepper and basil and stir/whisk.
Taste for seasoning (it should be just barely sweet. The basil and pepper will round it out)
Carve the tenderloin and drizzle the sauce over top.
