1. Heat a frying pan with about half the oil over medium-high heat. Add halloumi cubes and brown, flipping to ensure all sides are cooked. Allow to cool on a paper towel.
2. In a clean frying pan, heat remaining oil. Sauté onion, broccoli, and tomatoes for six minutes. Add the duck sauce, soy sauce, and garlic and cook for five minutes.
3. Place hot fettuccine in a bowl and add vegetable mixture and cheese cubes. Toss and serve hot (if pasta has already cooled, heat the whole mixture up together in a pot before serving).