Cook spaghetti according to package directions. Meanwhile, combine the cornstarch, broth, soy sauce, brown sugar, ginger and salt in a small bowl until smooth. Add pepper flakes if desired; set aside., Stir-fry pork in oil in a large skillet or wok for 4-6 minutes or until browned. Remove with a slotted spoon; keep warm. Stir-fry onion for 2 minutes. Add broccoli mixture; stir-fry 4-5 minutes longer or until vegetables are crisp-tender., Stir cornstarch mixture and add to the pan. Stir in peas. Bring to a boil; cook and stir for 3-4 minutes or until thickened. Drain spaghetti. Add pork and spaghetti to the pan; heat through.