Preheat the oven to 350°F.
Boil the macaroni in salted water for 2 minutes less than the package directions (the noodles will continue to cook when baked.) Drain the noodles and set aside.
In a large high-sided fry pan, skillet, or braiser, melt 4 tablespoons of the butter over medium-high heat. Whisk in the flour and curry powder and cook for 1 minute or until fragrant.
Add the cold milk to the flour mixture, whisking well to combine. Bring the mixture to a boil and cook for 4-5 minutes, whisking continuously as the mixture thickens. Stir in the salt and pepper then remove from the heat. Off of the heat, add the cheeses and stir until melted. Add the chicken, broccoli, and macaroni to the cheese mixture. Fold the ingredients together until well combined.
Melt the remaining 1 tablespoon of butter in a small pan or melt it in the microwave. Stir the butter into the panko bread crumbs. Sprinkle the bread crumbs over the mixture and bake for 15-20 minutes or until the macaroni and cheese is bubbling and the top is golden. Remove from the oven and allow the dish to rest for 5 minutes before serving.