In a pot or pan add the contents of the boxed mac and cheese, add the milk and water. Simmer for half the time on the packet's directions.
If using fresh broccoli, add it for the last 3–4 minutes of cooking time until tender but still vibrant green. Add the onion and peas now. If using frozen broccoli, microwave until thawed. Don't add frozen broccoli to the dish until later. Turn it down to the lowest setting for the remaining time.
Once the pasta is almost cooked but still has some liquid, add the shredded cheddar and parmesan. Then, add the garlic powder, onion powder, and black pepper. Stir until smooth and creamy.
Gently fold in the drained tuna. Add the cooked frozen broccoli now (if using frozen). Make sure everything is evenly coated in the creamy cheese sauce.
In a small bowl, mix the panko breadcrumbs and melted butter. Sprinkle over the mac and cheese.
Move the mac and cheese mixture to an oven-safe dish. Bake at 180℃ for 10 minutes. Continue until the top is golden brown and crispy. Watch closely to prevent burning.
Sprinkle with fresh parsley or chives for a pop of color and freshness. Serve immediately and enjoy your upgraded mac and cheese!