01 - Preheat oven to 375°F. Grease a 2.5-quart baking dish with butter or oil.
02 - Bring a large pot of salted water to a boil. Add macaroni and cook for 2 minutes less than the package recommends. Add broccoli florets during the last 2 minutes. Drain thoroughly and set aside.
03 - In a medium saucepan over medium heat, melt butter. Whisk in flour and cook for 1 to 2 minutes until lightly golden, stirring constantly.
04 - Gradually whisk in milk, continuing to stir until the sauce thickens, about 5 minutes. Remove from heat, then stir in cheddar, Gruyère, Dijon mustard, garlic powder, onion powder, nutmeg, salt, and black pepper until smooth and fully melted.
05 - Mix cooked macaroni and broccoli with the cheese sauce, ensuring even coating. Transfer this mixture into the prepared baking dish.
06 - In a small bowl, blend panko breadcrumbs, Parmesan cheese, and olive oil or melted butter. Evenly sprinkle over the macaroni mixture.
07 - Bake for 20 to 25 minutes until bubbly and golden on top. Allow to rest for 5 minutes before serving.