Cook the brown rice according to package directions in plenty of water with a pinch of salt, drain and keep warm. Slice the bok choy lengthwise into quarters and mince the garlic finely.
Season the pork tenderloin with salt and pepper. Heat half of the olive oil in a skillet and sear the meat on all sides; then fry on medium heat for about ten to twelve minutes until pink inside and let rest under foil.
Heat the remaining oil in a wok, briefly sauté the garlic and ginger and add the bok choy. Stir-fry for two to three minutes and deglaze with the tamari. Slice the pork tenderloin and serve with the bok choy and brown rice.