Preheat your oven to 400°F (200°C) and line a small baking sheet with parchment paper.
In a small bowl, whisk together the honey, tamari, hoisin sauce, toasted sesame oil, five spice powder, grated ginger, and minced garlic to create the marinade.
Pat the pork tenderloin dry with paper towels and season evenly with sea salt and black pepper.
Heat a cast-iron or oven-safe skillet over medium-high heat and sear the pork for 2 minutes on each side until a golden crust forms.
Brush half of the prepared char siu glaze over the pork and transfer the skillet (or move pork to the baking sheet) into the oven.
Roast for 12 to 15 minutes, brushing with the remaining glaze halfway through, until the internal temperature reaches 145°F (63°C).
While the pork roasts, steam the baby bok choy for 3 to 5 minutes until the stalks are tender but still have a slight crunch.
Remove the pork from the oven and let it rest for at least 5 minutes before slicing into medallions.
Serve the sliced pork drizzled with any remaining pan juices alongside the steamed bok choy.