Now, take a mixing bowl and combine soy sauce, vinegar, cornstarch, broth, sugar, salt and chili flakes. Mix these ingredients to form a smooth paste. Take a nonstick frying pan and add half cup of water and broccoli to it. Place the frying pan over high heat and bring the water to boil. Once the mixture comes to boil, reduce the heat to medium level and simmer the mixture. Cook until the broccoli becomes tender, and then drain the broccoli and keep it aside.