Remove the meat from the frig in time and let it come to room temperature.
Preheat the oven to 190°C.
Season the pork tenderloins with salt and pepper.
Heat the olive oil in an oven-proof skillet over medium-high heat.
Fry the pork tenderloins on both sides until golden brown, about 2 minutes per side.
Add the chopped garlic and thyme leaves (if desired) and cook for another 1 minute.
Cover the meat with alumnium foil in such a way that it does not dry out. Place the pan with the pork tenderloins in the preheated oven and bake for 15-20 minutes, depending on desired doneness. If necessary, use a meat thermometer to check the core temperature.
Remove the pan from the oven and add the butter. Melt the butter and baste the pork tenderloins with it.
Let the meat rest for 5 minutes before cutting. While resting, the core temperature will rise slightly more - 63°C for medium rare and 70°C for medium.