01 - Preheat oven to 375°F. Grease a 2.5-quart baking dish.
02 - Boil a large pot of salted water. Cook 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 for 1 to 2 minutes until lightly golden.
04 - Gradually whisk in milk and cook, whisking constantly, until thickened, about 5 minutes. Remove from heat and stir in cheddar, Gruyère, Dijon mustard, garlic powder, onion powder, nutmeg, salt, and pepper until smooth.
05 - Mix cooked macaroni and broccoli with cheese sauce until evenly coated. Transfer mixture to the prepared baking dish.
06 - Combine panko, Parmesan, and olive oil in a small bowl. Sprinkle evenly over the macaroni mixture.
07 - Bake for 20 to 25 minutes until bubbly and golden brown on top. Let rest 5 minutes before serving.