01 - Preheat oven to 375°F. Grease a 2.5-quart baking dish.
02 - Bring a large pot of salted water to a boil. Cook elbow macaroni for 2 minutes less than package instructions. Add broccoli florets during the last 2 minutes. Drain and set aside.
03 - Melt butter in a medium saucepan over medium heat. Whisk in flour and cook 1 to 2 minutes until lightly golden.
04 - Gradually whisk in whole milk. Cook, whisking constantly, until thickened, approximately 5 minutes.
05 - Remove from heat. Stir in cheddar, Gruyère, Dijon mustard, garlic powder, onion powder, nutmeg, salt, and black pepper until smooth and cheese is fully melted.
06 - Mix cooked macaroni and broccoli with cheese sauce until evenly coated. Transfer to prepared baking dish.
07 - In a small bowl, combine panko breadcrumbs, Parmesan cheese, and olive oil. Sprinkle evenly over the pasta mixture.
08 - Bake for 20 to 25 minutes until bubbling and golden brown on top. Allow to rest 5 minutes before serving.