Boil vinegar in a small saucepan over medium-high heat about 8 minutes or until liquid is reduced by two thirds and becomes syrupy. Watch carefully, as the reduction will occur very quickly towards the end of the cooking time. If overcooked, the reduction could scorch. Set aside. Add pork, red pepper, cauliflower, snow peas and broth to a medium skillet. Cook over medium-high heat, covered, stirring every 5 minutes, for 15 minutes or until vegetables are tender. Serve mixture warm over salad greens. Drizzle with balsamic glaze and sprinkle each with sunflower seeds. Season with freshly ground black pepper if desired.