In a small mixing bowl, whisk together the honey, tamari, hoisin sauce, sesame oil, five spice powder, grated fresh ginger, and minced garlic to create the char siu marinade.
Season the pork tenderloin with sea salt and black pepper, then place it in a shallow dish and coat with half of the prepared marinade, reserving the other half for later.
Allow the pork to marinate for at least 20 minutes, then preheat your oven to 400°F and line a baking sheet with parchment paper.
Place the pork on the baking sheet and roast for 20 to 25 minutes, or until the internal temperature reaches 145°F, brushing with the reserved marinade halfway through.
While the pork roasts, steam the halved baby bok choy for 4 minutes until the leaves are bright green and the stalks are tender-crisp.
Remove the pork from the oven and let it rest for 5 minutes before slicing into medallions.
Serve the sliced pork over a bed of warm cooked brown rice alongside the steamed bok choy, drizzling any remaining glaze from the pan over the top.