Preheat skillet to 350 degrees. Place steamer rack in skillet. Pour one inch of water in skillet. Remove tough stems from broccoli; wash, then cut heads into flowerets. Steam for 7-8 minutes, or until broccoli is tender but still crisp. Mix sesame oil with vinegar in a serving bowl. Add steamed broccoli and mix gently to coat. Sprinkle with sesame seeds and black pepper