In a bowl or large sealable plastic bag, combine the mirin, soy sauce, ginger, vinegar, and garlic. Season with pepper. Add the pork and coat well with the marinade. Cover the dish or seal the bag. Refrigerate for about 2 hours, or more. Drain the meat and keep the marinade.
In a large skillet or wok over high heat, sauté the meat in the oil, in two or three batches, until golden brown.
Set aside on a warm plate. Pour the marinade into the wok and let reduce until the sauce is syrupy.
Serve the meat over rice and top with the sauce. Serve with bok choy.
Mirin is a thick sweet rice wine, used mainly as an ingredient in Asian cuisine. It is sold in grocery stores in the Asian product aisle.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.