1. Heat a large wok over high heat until very hot. Toss pork with sesame oil, salt, and pepper. Add pork to pan; let stand 2 minutes, without stirring, so that pork gets crispy and browned. Stir-fry pork for 2 minutes or until well browned on all sides. Let stand 1 minute without stirring. Spoon pork into a bowl; set aside.
2. Reheat pan over high heat until very hot. Add canola oil; swirl to coat. Add bok choy; stir-fry 2 minutes. Add green beans, ginger, garlic, and bell pepper; stir-fry 3 minutes or until crisp-tender. Combine vinegar, soy sauce, and brown sugar, stirring until sugar dissolves. Remove pan from heat; stir in vinegar mixture, tossing to coat. Stir in pork. Sprinkle with green onions. Serve over rice.