01 - Preheat your oven to 375°F. Grease a 9x13 inch baking dish with butter or cooking spray.
02 - Bring a large pot of salted water to a boil. Add macaroni and cook for 6 minutes. Add broccoli florets and cook both together for an additional 2 minutes, until pasta is al dente and broccoli is bright green. Drain well and set aside.
03 - In a large saucepan, melt 4 tbsp butter over medium heat. Stir in flour and cook for 2 minutes, stirring constantly to create a smooth roux.
04 - Gradually whisk in milk and heavy cream. Continue cooking and whisking until sauce thickens and bubbles, approximately 5 minutes.
05 - Remove saucepan from heat. Stir in sharp cheddar, Gruyère, Dijon mustard, garlic powder, onion powder, salt, and black pepper until completely smooth and creamy.
06 - Add cooked macaroni and broccoli to the cheese sauce. Mix thoroughly until evenly coated. Transfer mixture to the prepared baking dish.
07 - In a small bowl, combine panko breadcrumbs, grated Parmesan, and melted butter. Mix well to ensure butter coats all crumbs evenly.
08 - Sprinkle breadcrumb mixture evenly over the macaroni. Bake for 20-25 minutes until sauce bubbles and topping turns golden brown. Allow to rest for 10 minutes before serving.