Preheat your oven to 400°F (200°C).

Pat the beef tenderloin dry with paper towels. Season it generously with salt and black pepper on all sides.

Using a mortar and pestle or a rolling pin, crack the Szechuan peppercorns into smaller pieces.

In a dry skillet over medium heat, toast the sesame seeds until golden brown and fragrant, about 3-4 minutes. Stir frequently to prevent burning. Remove from heat and let cool.

In a small bowl, mix the cracked Szechuan peppercorns and toasted sesame seeds. Rub the vegetable oil over the tenderloin and then roll it in the peppercorn-sesame mixture, pressing gently to adhere.

Heat a cast-iron skillet over high heat. Once hot, add the tenderloin and sear for 2-3 minutes on each side until browned all over.

Transfer the skillet to the preheated oven and roast the tenderloin for about 15-20 minutes, or until it reaches your desired level of doneness (130°F for medium-rare).

While the tenderloin is roasting, in a small bowl, combine the softened butter, mashed black garlic, fresh thyme, and a pinch of salt. Mix until well combined.

Once the tenderloin is done, remove it from the oven and let it rest for 10 minutes. This allows the juices to redistribute.

Slice the tenderloin into medallions and serve with a dollop of black garlic butter on top. Enjoy!